Hard to offer help, I would back up anything you want to save and try this:
Go to Settings>update & Security>Recovery>Advanced Start up (If this method doesn't restart pc, tapping F8 at start up will bring you to same menu)
This should restart pc and load you into Advanced Start, here I would choose Troubleshoot, and then choose reset this PC & save files.
Ideally this would save all your files (but not apps) and reinstall Windows 10. With your sick system this might not even work . Hence why i said back up everything
But you don't want to reinstall apps which to me would be faster than messing around trying to fix the pc. especially if you don't know what is wrong.
You also get command prompt here but I don't think you have admin rights since you aren't actually logged into windows... so doubt you can do much.
Alternate is try system restore back to a time you could do things, or was that never?
Some things best solved with a fresh install.