delete account


You can't delete an account. You can close it if you want.
It's frustrating to lose a lot when you start out. However, the rating system is designed to help match you with players of similar strength. Your rating in rapid is now around 800. Those players often display a good knowledge of chess fundamentals. If you have studied chess fundamentals yourself, the chances are good that if you continue for a while, you will find the right level.
If you haven't taken the time, have you tried any of the lessons here for beginners? They can be really helpful. https://www.chess.com/lessons/opening-principles
If you still want to close your account,
https://support.chess.com/article/363-how-do-i-close-my-account