How to recover an account in Mac OS?

Question

macOS

Good afternoon. Faced a problem.
On Mac OS High Sierra, I changed the account (its name). I went into the settings, accounts, right-clicked "Advanced options" made my changes and rebooted the computer. After the reboot, I entered my data and logged into the system.
But now it's a mistake. Every time I do an action where I need to enter a password for confirmation, a window pops up for me where it requires me to enter the account name and password (previously, the account was simply set automatically and only the password had to be entered). Whatever account I try to enter, new or old, nothing works, does not want to use it.
How can I restore old data? What to do in such a situation? Reinstall operating system? Help advice.