I can't open files from desktop

Try rebuilding your Finder Preferences and see if that helps.

From your Finder "Go" menu > "Go to folder" then copy & paste this file path:

~/Library/Preferences/com.apple.finder.plist

Click Go.

Delete the plist file.

Then, restart, or log out and in again.

(You may have to reset some Finder preferences the way you like them)

What happens when you try?

Good luck...