then he deleted his telegram account where we had our conversation (his telegram acount was @AyungP). Now when i search @AyungP, it doesn't even exist. But if you look at https://bitcointalk.org/index.php?topic=5262855, that's his telegram account
I don't think there's much we can help you with here. You should've used escrow though through someone trusted on the forum (fter verifying their identity).
If you post proof of telegram messages and the transactions involved (unless he deleted them with the account)...
yep. the telegram messages were gone because he deleted his telegram account