I only use HA Telegram broadcast. For Telegram interaction I use Node-Red (link), Your polling config looks good to me, as far as I can tell. 
I do not have experience setting up interaction with HA, but I read the component docs, linked in my previous answer.
So, if you use polling and a Telegram answer message starts with
/
then you probably need an event triggering to, ehh, trigger an event…
Also, as far as the none Home Assistant part, you don’t need extra config to communicate with Telegram, no need for port forwarding, dynamic DNS config, etcetera… If sending a message works, then sending back commands should be working also.
I don’t know if sending a message without / will work, I don’t think so, but I’m not sure about that…
Can anyone, with more experience, please jump in?