Log into your server with root privileges. Then start a Ruby on Rails console.
Start the console with this command:
Wait until the console has loaded.
There are multiple ways to find your user. You can search for email or username.
or
Now you can change your password:
It’s important that you change both password and password_confirmation to make it work.
Don’t forget to save the changes.
Exit the console and try to login with your new password
https://docs.gitlab.com/ee/security/reset_root_password.html