i m beginner. i changed usr folders chmod to 777. after restart wifi adapter not working. And /usr/bin/sudo must be owned by uid 0 error seen in terminal. i cant mount i cant type code because i get this error. please help me to fix this problem

So first as an advise to a beginner, do not run commands you do not know what this one is actually doing.
You changed the permission of all files inside /usr, the only thing I can think about trying is chroot into your install https://getsol.us/articles/troubleshooting/boot-rescue/en/#mounting-your-system and run chmod 755 on /usr and pray to god this fixes your system.

the other is pull a backup of your important files and reinstall your system, would be the simplest solution for a beginner

Like @Girtablulu said, backup and restore, fixing this system would be painful and time-consuming. Try not to run random commands you find online, permissions are a fickle thing.