Hi XYOG TM,
Thank you for Posting in Microsoft Community.
I'm sorry to hear about the issue you're experiencing. It seems like changing the administrator account settings may have caused the black screen problem. To resolve this, you can try booting your laptop into Safe Mode by pressing F8 or Shift + F8 during startup. From there, you can try to revert the changes you made to the administrator account settings. If that doesn't work, you may need to perform a system restore to a point before you made the changes. If you're unable to resolve the issue.
Before doing the steps make sure you have backed up files.
If you want to change into new Microsoft account as a user then how about you create a new user. It seems that the user you have is corrupted.
To do that > press windows key and I then it opens settings > account > other users> create new user then add the Microsoft account then click the newly created user profile then put admin and restart or sign out by pressing windows key then click the user name of your current profile then signout to switch to a new user.
Best Regards,
Bench
Microsoft Moderator