Cheating?

How many moves ?
If it's a gambit and you fell for it, it's possible.
Else it's probably cheating, yes.
edit: i checked that game. Highly suspicious. You did make some dubious moves but the string of perfect moves is sketchy. 25 moves and 19 were best, 3 book. That leaves 3 moves which were: great, excellent and good.
No inaccuracy, no mistake, no miss...highly unlikely at that level.
Also, i don't think 600 elo players find those moves at the end, especially the bishop sac.

Solving the mate in 9 was suspicious

Yeah, i checked his profile, he has a string of 91+ rated games (most are 97/98 ~ ).
Think he got mad and started cheating or something haha. I reported him.

If you suspect another member is using disallowed resources you should report them

https://support.chess.com/article/648-what-do-i-need-to-know-about-fair-play-on-chess-com

https://www.chess.com/article/view/online-chess-cheating

https://www.chess.com/article/view/chesscom-update-may-2024?#FairPlay

The site closed 56,000+ accounts in April for fair play violations and has a full team of staff working on reports along with some automated systems for detection.

https://www.chess.com/article/view/fair-play

That said, discussions of cheating, potential cheating, or cheat detection are not allowed in the general forums. If you would like to discuss join the following club. https://www.chess.com/club/cheating-forum