How to receive messages in group chats using telegram bot api
Solution 1:
Talk to @botfather and disable the privacy mode.
Solution 2:
Sequence within a BotFather chat:
You: /setprivacy
BotFather: Choose a bot to change group messages settings.
You: @your_name_bot
BotFather: 'Enable' - your bot will only receive messages that either start with the '/' symbol or mention the bot by username.
'Disable' - your bot will receive all messages that people send to groups.
Current status is: ENABLED
You: Disable
BotFather: Success! The new status is: DISABLED. /help