Someone reported me by sandbagging

I Played the game really poor ( IT was bullet) and my opponent said he will report me by sandbagging... Will my acc get banned?

No

Ja!

No, if everyone who played badly got banned for sandbagging, there would be no one left playing here.

Sandbagging is only relevant if the sandbagger intends to play in full-on competitions anyway. You can't "sandbag" to get higher ratings here, because you only get points by winning, and although you can get to play lower-rated opponents by losing a lot, you still can't get to be a higher-rated person without winning against people at that rating. If you sand-bag your way down the ladder, all you have to do is climb back up again by winning against people rated the same as you just lost against, so it's self-defeating!

Also loads of people (me included) go into losing-streaks after a nasty lose, where they look like they're sandbagging, but actually they are just depressed, self-destructive, and in a rage-quit/who-cares-I'm-useless frame of mind; fortunately, having negative self-image is not an offence here.

Sandbagging is intentional, repeated loss to artificially lower one’s rating. A bad game IS NOT SANDBAGGING. You are safe. Do not worry if you did not do anything wrong.