My friend not cheat, but he got banned !

You are trying to "Prove" that because your friend is talented, he wouldn't cheat? Reality is: Many good players do cheat, because their talent makes them feel entitled to winning.

Thank Duong Vu Anh!

I contacted lichess.org/appeal. They will definitely check again. Do not worry

other things that might have happend:
1.hacked or scammed
2.@lichess accidently presses the wrong button