MacBook not opening apps
Even before trying to fix permissions - I would make a new user account and then see if you can open these three apps:


Calculator - check if self-contained apps work
Safari - check if networking works
Calendar - check something that can connect to cloud data - substitute contacts if you don't sync calendars. Mail is usually a huge amount to download - so that's generally a bad test app.


If your new account works, the system and online and network are fine and it's just your settings in your user account that are amiss (or third party apps). If you can't make a new user work - then consider wiping the Mac and restoring from your backup once you have a clean install.