How do I use Recovery to get my Mac working PROPERLY again?

Recovery is a stripped-down macOS that’s kept hidden for emergencies. To enter Recovery, restart or power up your Mac and immediately hold down Cmd-R until you see the Apple logo. If Recovery fails, you’ll see a globe instead, meaning your Mac is trying to recover by downloading tools (you can force this by holding Opt-Cmd-R while starting up).

Either way, you get four options: Restore From Time Machine Backup (if you have one); Reinstall macOS; Get Help Online (browse Apple Support); and Disk Utility. Reinstalling macOS may fix things without deleting your data. Restoring from Time Machine is more drastic, but just as easy – it may take a number of hours, but should get you back to normal.