At the log in screen.....
Hold the shift key and use the Power Button options to click "Restart"
That should loop you into the advance trouble shooting options from which you can boot into Safe Mode.
See if boot into safe mode produces the same problem.
Some of the screens you will see are described in this article here
https://www.windows10forums.com/articles/safe-mode.3/
Except the initial restart process the rest should be the same.
Choose Option #4 or #5 if you need networking. This is just a test so networking may not be needed.
I don't suspect a virus.
See if the login screen has any icon indicating a language choice option sometimes the update changes the keyboard layout.
Are you certain that the user name you are seeing at the login screen is correct? Do you see any link that may reference "I'm not" OR "Not Me"?
When you say "I don't have a password" .......
What account are you using to log in with? I assume a local account rather than a Microsoft Account. Do you have any other user accounts configured on this computer.