Mac Os update

Hi guys. I m using macbook

pro late 2013. I m a beginner when it comes to mac. Apparently, i cant update my mac it’s still in OS X Mavericks app store isn’t working. Also, apple support site can’t be reached. I’ve tried the recovery boot to reinstall mac os big sur but “ the recovery server should not be contacted “ always popped up. I duno what to do next