I fixed the issue by reversing the steps I did in the Registry. I won't touch it again!
Thank you very much for your help!

>In these articles the "command prompt" is what you get in the Recovery environment. I edited my first reply, you might try the second link there.
>
>>The URL/article says to get to the Command prompt. But I cannot get to the command prompt. All I can get to is RegEdit. Then, if I can find the Registry backup file I just created (a few minutes ago) maybe the problem will be fixed.
>>
>>>If you have a recent restore point, you might be able to use that: https://answers.microsoft.com/en-us/windows/forum/all/windows-10-changed-regedit-and-cant-login/d653eedb-f3ce-493a-a37a-b8e28790732b
>>>
>>>If that doesn't work there are other options at https://theitbros.com/restore-windows-10-registry-from-backup-or-restore-point/ , use at your own risk.
>>>
>>>>Hi,
>>>>
>>>>I am trying to make the Users folder to "Dmitry" from "Litva" The strange thing is that I see it correctly in the Windows Explorer and the Computer Management window. In those windows it says "Dmitry" And yet if I go to the command prompt and the folder Users, the only folders I see are Litva and Public. I find it strange that in one place it is Dmitry (the way I want it) but the actual folder name is different.
>>>>
>>>>How do I change the actual folder name from Litva to Dmitry?
>>>>
>>>>TIA
>>>>
>>>>UPDATE. I think I messed up my Windows 10 big time. I went to the registry and found the ProfileImagePath and renamed the folder name from Litva to Dmitry Now I cannot even log in into my PC :(
>>>>
>>>>UPDATE 2. I made a backup of the registry before I made the change. But I cannot even get to the Registry so that I can import the backup copy. Anybody knows how to get there? TIA