when i was racing i pressed something accidently and my screen looks like a mirror. like this: please quickly tell me the fix because i want to race

And what is wrong there?

The screen is like reduced quality? i checked graphics settings,nothings wrong.

Have you checked under "Screen" in options. Make sure that it's at the highest resolution that your monitor/sysytem can handle.

Issue Solved. it was somethings wrong with resolution.

There are key combos in LFS by default that change to the more common resolutions. It's likely you hit one of those keys.