Take these steps first.... I will add more to this guide throughout the day I made these for a friend who needed to get PSO2 working which he did.
(1): 'After uninstalling game I'm still missing gigabytes!' : After uninstalling usually you restart and the space comes back.
If not you can take control of the Windows Apps folder and delete it yourself. (Right click on folder- Properties - Security - Advanced - Owner Change in the check names box put either the user name of the account to log into the computer or Everyone Hit check names & Hit ok and check box Replace all objects and wait.) You should be able to access the folder and delete what you want out of it.
(2): 'Windows Store is giving me Errors or won't boot at all!' : Again Windows 10 updates can get corrupted I know it's stupid but whatever you can fix it By 1 of 5 ways and the last two you don't want...
1: Run SFC/Scannow: this command will usually find and fix integrity violations in the windows system. (Right click on the start menu icon - Search - CMD - in the results run as admin - type sfc /scannow and wait if there are any problems it will find and fix them.)
2: Run DISM: Same thing when accessing CMD prompt in the first option except instead of SFC you type:
DISM /Online /Cleanup-Image /CheckHealth or DISM /Online /Cleanup-Image /ScanHealth it will scan and you wait then if it finds errors type DISM /Online /Cleanup-Image /RestoreHealth. Hit enter and wait.
3: WSreset, this should be used with the other two options just to clean the store up. (Right click on the start menu icon - Search - wsreset, when it shows up click run as admin.)
4: When all else fails, system reset. There are guides on the net for this, it will let you keep your files and some programs but it will erase and reinstall everything else.
5: Last but not least reinstalling Windows 10 itself. The worst and very last option should SFC or DISM find violations and either fail to repair them or they don't work. If you do, and some people will and some won't there are guides on how to make a USB using Win 10 creation tool. (8gb minimum space required) If this option is for you I would recommend not linking your MS account to Windows ever for login. Use a local account instead and sign in to just the apps!
(3)User Account Errors or bad permissions for PSO2: Whenever you make an account with windows I would recommend to make a local account and don't sign into microsoft. If you do sign in with MS, go to manage your settings in Windows and turn off account sync for PC'. Syncing settings from past PC's or builds usually messes windows up in my experience.
(4) Laggy PSO2 fix: https://www.reddit.com/r/PSO2/comments/gsn90o/workaround_fix_unbearable_lobby_lag/