diff --git a/bot.py b/bot.py
index 8fd4597..aad1d5f 100644
--- a/bot.py
+++ b/bot.py
@@ -34,20 +34,28 @@ def on_chat(msg):
         # pre-treat the command
         command = [msg['text']]
         if msg['text'][0] == '/':
-            command = msg['text'].replace('_', ' ').lower().split(' ')
-            command[0] = command[0].replace(config.NAME, '')
+            command = msg['text'].replace(config.NAME, '').replace('_', ' ').lower().split(' ')
 
         # first-time user
-        if user.status == '第一次用' and chat_type == 'private':
-            user.new_user()
+        if user.status == '第一次用':
+            if chat_type == 'private':
+                user.new_user()
+            else:
+                bot.sendMessage(chat_id, "請先私訊我登入 kCOJ", reply_to_message_id=msg['message_id'])
 
         # press password
-        elif user.status == '輸入學號' and chat_type == 'private':
-            user.press_password(msg['text'])
+        elif user.status == '輸入學號':
+            if chat_type == 'private':
+                user.press_password(msg['text'])
+            else:
+                bot.sendMessage(chat_id, "請先私訊我登入 kCOJ", reply_to_message_id=msg['message_id'])
 
         # login
-        elif user.status == '輸入密碼' and chat_type == 'private':
-            user.login_kcoj(msg['text'])
+        elif user.status == '輸入密碼':
+            if chat_type == 'private':
+                user.login_kcoj(msg['text'])
+            else:
+                bot.sendMessage(chat_id, "請先私訊我登入 kCOJ", reply_to_message_id=msg['message_id'])
 
         elif user.status == '舊的密碼' and chat_type == 'private':
             if user.check_online() == True:
@@ -60,30 +68,17 @@ def on_chat(msg):
         elif user.status == '上傳答案' and chat_type == 'private':
             if user.check_online() == True:
                 user.send_answer(msg['text'], '')
-
+        
         elif command[0] == '/start' or command[0] == '首頁🏠':
             if user.check_online() == True:
-                user.display_main()
+                user.display_main(chat_id)
 
         elif command[0] == '/question' or command[0] == '題庫📝' or command[0] == '更新🔃':
             if user.check_online() == True:
                 if len(command) > 1:
-                    user.display_question(command[1])
+                    user.display_question(chat_id, command[1])
                 else:
-                    user.display_questions()
-
-        elif command[0] == '/help' or command[0] == '幫助📚':
-            if user.check_online() == True:
-                user.help_you()
-
-        elif command[0] == '/password' or command[0] == '改密碼💱':
-            if user.check_online() == True:
-                user.press_oldpassword()
-
-        elif command[0] == '/logout' or command[0] == '登出🚪':
-            user = kuser(from_id, bot)
-            users[str(from_id)] = user
-            user.logout_system()
+                    user.display_questions(chat_id)
 
         elif command[0] == '/restart':
             if str(from_id) in config.ADMIN:
@@ -92,16 +87,29 @@ def on_chat(msg):
                 time.sleep(1)
                 os._exit(0)
 
+        elif (command[0] == '/help' or command[0] == '幫助📚') and chat_type == 'private':
+            if user.check_online() == True:
+                user.help_you()
+
+        elif (command[0] == '/password' or command[0] == '改密碼💱') and chat_type == 'private':
+            if user.check_online() == True:
+                user.press_oldpassword()
+
+        elif (command[0] == '/logout' or command[0] == '登出🚪') and chat_type == 'private':
+            user = kuser(from_id, bot)
+            users[str(from_id)] = user
+            user.logout_system()
+
         elif user.question != '題外':
             if user.check_online() == True:
-                if command[0] == '/upload' or command[0] == '交作業📮':
+                if (command[0] == '/upload' or command[0] == '交作業📮') and chat_type == 'private':
                     user.upload_answer()
-                elif command[0] == '/result' or command[0] == '看結果☑️':
+                elif (command[0] == '/result' or command[0] == '看結果☑️') and chat_type == 'private':
                     user.list_results()
-                elif command[0] == '/passer' or command[0] == '通過者🌐':
+                elif (command[0] == '/passer' or command[0] == '通過者🌐') and chat_type == 'private':
                     user.list_passers()
                 elif command[0] == '回題目📜':
-                    user.display_question(user.question)
+                    user.display_question(chat_id ,user.question)
 
     elif content_type == 'document':
         if user.status == '上傳答案' or user.status == '查看題目':
diff --git a/interface.py b/interface.py
index 316f604..41cbf8f 100644
--- a/interface.py
+++ b/interface.py
@@ -10,8 +10,8 @@ import access
 import config, promote
 
 class kuser:
-    def __init__(self, chat_id, bot):
-        self.chat_id = chat_id
+    def __init__(self, from_id, bot):
+        self.from_id = from_id
         self.bot = bot
         self.username = ''
         self.password = ''
@@ -26,19 +26,19 @@ class kuser:
     def press_username(self):
         self.status = '輸入學號'
         self.question = '題外'
-        self.bot.sendMessage(self.chat_id, "請輸入您的學號：", reply_markup=ReplyKeyboardRemove())
+        self.bot.sendMessage(self.from_id, "請輸入您的學號：", reply_markup=ReplyKeyboardRemove())
 
     def press_password(self, text):
         self.status = '輸入密碼'
         self.question = '題外'
         self.username = text
-        self.bot.sendMessage(self.chat_id, "輸入完可刪除訊息以策安全！\n"
+        self.bot.sendMessage(self.from_id, "輸入完可刪除訊息以策安全！\n"
                                            "請輸入您的密碼：", reply_markup=ReplyKeyboardRemove())
 
     def press_oldpassword(self):
         self.status = '舊的密碼'
         self.question = '題外'
-        self.bot.sendMessage(self.chat_id, "請輸入要原本的舊密碼：",
+        self.bot.sendMessage(self.from_id, "請輸入要原本的舊密碼：",
             reply_markup=ReplyKeyboardMarkup(keyboard=[
                 ["首頁🏠"]
             ], resize_keyboard=True))
@@ -47,19 +47,19 @@ class kuser:
         self.status = '修改密碼'
         self.question = '題外'
         if text != self.password:
-            self.display_main()
+            self.display_main(self.from_id)
         else:
-            self.bot.sendMessage(self.chat_id, "使用此功能請務必小心！\n"
+            self.bot.sendMessage(self.from_id, "使用此功能請務必小心！\n"
                                                "請輸入要設定的新密碼：", reply_markup=ReplyKeyboardRemove())
         
     def change_password(self, text):
         self.status = '正常使用'
         self.question = '題外'
         if text == "首頁🏠":
-            self.display_main()
+            self.display_main(self.from_id)
         else:
             self.password = text
-            self.bot.sendMessage(self.chat_id, "修改成功" if self.api.change_password(self.password) == True else "修改失敗",
+            self.bot.sendMessage(self.from_id, "修改成功" if self.api.change_password(self.password) == True else "修改失敗",
                 reply_markup=ReplyKeyboardMarkup(keyboard=[
                     ["首頁🏠"]
                 ], resize_keyboard=True))
@@ -68,14 +68,14 @@ class kuser:
         self.status = '正常使用'
         self.question = '題外'
         self.password = text
-        self.bot.sendMessage(self.chat_id, "登入中...", reply_markup=ReplyKeyboardRemove())
+        self.bot.sendMessage(self.from_id, "登入中...", reply_markup=ReplyKeyboardRemove())
         if self.check_online() == True:
-            self.display_main()
+            self.display_main(self.from_id)
 
     def fail_login(self):
         self.status = '正常使用'
         self.question = '題外'
-        self.bot.sendMessage(self.chat_id, "哇...登入失敗，讓我們重新開始一次", reply_markup=ReplyKeyboardRemove())
+        self.bot.sendMessage(self.from_id, "哇...登入失敗，讓我們重新開始一次", reply_markup=ReplyKeyboardRemove())
         self.press_username()
 
     def check_online(self): # edit
@@ -83,7 +83,7 @@ class kuser:
         result = self.api.check_online()
         if result == None:
             self.question = '題外'
-            self.bot.sendMessage(self.chat_id, "郭老 Online Judge 離線中！",
+            self.bot.sendMessage(self.from_id, "郭老 Online Judge 離線中！",
                 reply_markup=ReplyKeyboardMarkup(keyboard=[
                     ["首頁🏠"]
                 ], resize_keyboard=True))
@@ -101,10 +101,10 @@ class kuser:
     def logout_system(self):
         self.status = '正常使用'
         self.question = '題外'
-        self.bot.sendMessage(self.chat_id, "您現在已經是登出的狀態。", reply_markup=ReplyKeyboardRemove())
+        self.bot.sendMessage(self.from_id, "您現在已經是登出的狀態。", reply_markup=ReplyKeyboardRemove())
         self.press_username()
 
-    def display_main(self):
+    def display_main(self, chat_id):
         self.status = '正常使用'
         self.question = '題外'
         q_dict = self.api.list_questions()
@@ -114,7 +114,7 @@ class kuser:
                 q_str += "📗<b>" + key + "</b> (DL: " + q_dict[key][0] + ")\n [[" + q_dict[key][2] + "]]"
                 q_str += "⚠️" if q_dict[key][2] == '未繳' else "✅"
                 q_str += "  /question_" + key + "\n\n"
-        self.bot.sendMessage(self.chat_id, "💁 <b>" + self.username + "</b> " + config.NAME + "\n"
+        self.bot.sendMessage(chat_id, "💁 <b>" + self.username + "</b> " + config.NAME + "\n"
                                            "➖➖➖➖➖\n"
                                            "📝<i>可繳交的作業</i>\n\n" + q_str + \
                                            "➖➖➖➖➖\n" + choice(promote.sentences),
@@ -122,9 +122,9 @@ class kuser:
                                            reply_markup=ReplyKeyboardMarkup(keyboard=[
                                                ["題庫📝"],
                                                ["登出🚪", "改密碼💱", "幫助📚"]
-                                           ], resize_keyboard=True))
+                                           ], resize_keyboard=True) if chat_id == self.from_id else ReplyKeyboardRemove())
 
-    def display_questions(self):
+    def display_questions(self, chat_id):
         self.status = '正常使用'
         self.question = '題外'
         q_dict = self.api.list_questions()
@@ -134,7 +134,7 @@ class kuser:
             q_str += "<b>" + key + "</b> (DL: " + q_dict[key][0] + ")\n [[" + q_dict[key][2] + "]]"
             q_str += "⚠️" if q_dict[key][2] == '未繳' else "✅"
             q_str += "  /question_" + key + "\n\n"
-        reply = self.bot.sendMessage(self.chat_id, "💁 <b>" + self.username + "</b> " + config.NAME + "\n"
+        reply = self.bot.sendMessage(chat_id, "💁 <b>" + self.username + "</b> " + config.NAME + "\n"
                                                    "➖➖➖➖➖\n"
                                                    "📝<i>所有作業</i>\n\n" + q_str + \
                                                    "➖➖➖➖➖\n" + choice(promote.sentences),
@@ -142,10 +142,10 @@ class kuser:
                                                    reply_markup=ReplyKeyboardMarkup(keyboard=[
                                                        ["首頁🏠", "更新🔃"],
                                                        ["登出🚪", "改密碼💱", "幫助📚"]
-                                                   ], resize_keyboard=True))
-        self.bot.sendMessage(self.chat_id, "點我到題庫頂", reply_to_message_id=reply['message_id'])
+                                                   ], resize_keyboard=True) if chat_id == self.from_id else ReplyKeyboardRemove())
+        self.bot.sendMessage(self.from_id, "點我到題庫頂", reply_to_message_id=reply['message_id'])
 
-    def display_question(self, number):
+    def display_question(self, chat_id, number):
         self.status = '查看題目'
         self.question = number
         content = self.api.show_question(number)
@@ -155,18 +155,18 @@ class kuser:
         q_str += "📗" if q[1] == '期限未到' else "📕"
         q_str += "*" + number + "* (DL: " + q[0] + ")\n [[[" + q[2] + "]]]"
         q_str += "⚠️" if q[2] == '未繳' else "✅"
-        reply = self.bot.sendMessage(self.chat_id, q_str + "\n\n```\n" + content + "\n```",
+        reply = self.bot.sendMessage(chat_id, q_str + "\n\n```\n" + content + "\n```",
             parse_mode='Markdown',
             reply_markup=ReplyKeyboardMarkup(keyboard=[
                 ["首頁🏠", "題庫📝"],
                 ["交作業📮" if q[1] == '期限未到' else '', "看結果☑️" if q[2] == '已繳' else '', "通過者🌐"],
                 ["登出🚪", "改密碼💱", "幫助📚"]
-            ], resize_keyboard=True))
-        self.bot.sendMessage(self.chat_id, "點我到題目頂", reply_to_message_id=reply['message_id'])
+            ], resize_keyboard=True) if chat_id == self.from_id else ReplyKeyboardRemove())
+        self.bot.sendMessage(chat_id, "點我到題目頂", reply_to_message_id=reply['message_id'])
 
     def help_you(self):
         self.question = '題外'
-        self.bot.sendMessage(self.chat_id, "這裡是 kC Online Judge Bot！\n"
+        self.bot.sendMessage(self.from_id, "這裡是 kC Online Judge Bot！\n"
                                            "可以簡稱 kCOJ Bot，目前定居於 [" + config.NAME + "]\n"
                                            "作用是讓大家可以方便的透過我使用郭老程設課的 Online Judge\n"
                                            "➡️[傳送門](" + config.URL + ")\n"
@@ -198,7 +198,7 @@ class kuser:
         q_str += "📗" if q[1] == '期限未到' else "📕"
         q_str += "<b>" + self.question + "</b> (DL: " + q[0] + ")\n [[" + q[2] + "]]"
         q_str += "⚠️" if q[2] == '未繳' else "✅"
-        self.bot.sendMessage(self.chat_id, q_str + "\n\n現在請把你的程式碼讓我看看（請別超過 20 MB）\n"
+        self.bot.sendMessage(self.from_id, q_str + "\n\n現在請把你的程式碼讓我看看（請別超過 20 MB）\n"
                                                    "可以使用「文字訊息」或是「傳送檔案」的方式", parse_mode='HTML',
                                                    reply_markup=ReplyKeyboardMarkup(keyboard=[
                                                        ["刪除作業⚔️"] if self.api.list_questions()[self.question][2] == '已繳' else [],
@@ -210,14 +210,14 @@ class kuser:
         if text != '':
             if text == '首頁🏠':
                 if self.check_online() == True:
-                    self.display_main()
+                    self.display_main(self.from_id)
                     return
             elif text == '回題目📜':
                 if self.check_online() == True:
                     self.display_question(self.question)
                     return
             elif text == '刪除作業⚔️':
-                self.bot.sendMessage(self.chat_id, "移除成功" if self.api.delete_answer(self.question) == True else "移除失敗",
+                self.bot.sendMessage(self.from_id, "移除成功" if self.api.delete_answer(self.question) == True else "移除失敗",
                     reply_markup=ReplyKeyboardMarkup(keyboard=[
                         ["首頁🏠", "回題目📜"],
                         ["登出🚪", "改密碼💱", "幫助📚"]
@@ -231,14 +231,14 @@ class kuser:
             self.bot.download_file(file_id, self.username + self.question + '.c')
         self.api.delete_answer(self.question)
         if self.api.upload_answer(self.question, self.username + self.question + '.c') == True:
-            self.bot.sendMessage(self.chat_id, "上傳成功",
+            self.bot.sendMessage(self.from_id, "上傳成功",
                 reply_markup=ReplyKeyboardMarkup(keyboard=[
                     ["首頁🏠", "回題目📜"],
                     ["看結果☑️"],
                     ["登出🚪", "改密碼💱", "幫助📚"]
                 ], resize_keyboard=True))
         else:
-            self.bot.sendMessage(self.chat_id, "上傳失敗",
+            self.bot.sendMessage(self.from_id, "上傳失敗",
                 reply_markup=ReplyKeyboardMarkup(keyboard=[
                     ["首頁🏠", "回題目📜"],
                     ["登出🚪", "改密碼💱", "幫助📚"]
@@ -247,7 +247,7 @@ class kuser:
     
     def fail_send(self):
         self.status = '正常使用'
-        self.bot.sendMessage(self.chat_id, "檔案不能超過 20 MB！上傳失敗",
+        self.bot.sendMessage(self.from_id, "檔案不能超過 20 MB！上傳失敗",
             reply_markup=ReplyKeyboardMarkup(keyboard=[
                 ["首頁🏠", "回題目📜"],
                 ["登出🚪", "改密碼💱", "幫助📚"]
@@ -264,13 +264,13 @@ class kuser:
         q_str += "<code>\n"
         for passer in self.api.list_passers(self.question):
             q_str += "\n" + passer
-        reply = self.bot.sendMessage(self.chat_id, q_str + "</code>", 
+        reply = self.bot.sendMessage(self.from_id, q_str + "</code>", 
             parse_mode='HTML',
             reply_markup=ReplyKeyboardMarkup(keyboard=[
                 ["首頁🏠", "回題目📜"],
                 ["登出🚪", "改密碼💱", "幫助📚"]
             ], resize_keyboard=True))
-        self.bot.sendMessage(self.chat_id, "點我到名單頂", reply_to_message_id=reply['message_id'])
+        self.bot.sendMessage(self.from_id, "點我到名單頂", reply_to_message_id=reply['message_id'])
 
     def list_results(self):
         self.status = '正常使用'
@@ -283,7 +283,7 @@ class kuser:
             q_str += "\n測試編號 <code>" + result[0] + "</code>："
             q_str += "✔️ " if result[1] == '通過測試' else "❌ "
             q_str += result[1]
-        self.bot.sendMessage(self.chat_id, q_str, 
+        self.bot.sendMessage(self.from_id, q_str, 
             parse_mode='HTML', 
             reply_markup=ReplyKeyboardMarkup(keyboard=[
                 ["首頁🏠", "回題目📜"],