I can't download apps from appstore or log in connect on icloud without going to the web page

I have now changed my password so many times because i have been trying to fix it, only causing it to get worse. i have too many passwords i cant use anymore because i have had to change it in the belief that that was the problem. But no, it turns out that even when i am entering the right password "the action couldn't be done. Try again". The message pops up every single time when i enter the right password. This problem is both on app store and on the security and privacy protection on settings. Icloud can be logged in when on web page though, but there are so many things i can't do on the mac because of this stupid thing. Everything happened after i upgraded the macbook pro. I should just have kept it the way it was when i first bought it.