Hi there, aliakhtari2!
Thanks for reaching out to the Apple Support Communities! It sounds like you're seeing an error message when you try to create an account on your Mac. Does this issue happen when trying a different user name or password combination?
Let's try booting into safe mode to see if there is any difference. Check out this article with steps to follow for How to use safe mode on your Mac. This will perform checks and stop certain software from starting up automatically. Once you are in safe mode, test to see if you have the same issue.
If the issues continue, we would recommend reaching out to Apple directly by checking out this link to Get Support and they will be more than happy to proceed with additional steps.
Cheers!