How do I remove my ex's account from my MacBook?

My translation tool does not work with images so I have no idea what that says.

If you have administrator status on the Mac you can delete the account as described in this support document:

Delete a user or group on Mac - Apple Support

If you have no own user account on the Mac as an administrator, you can't delete the user account:

If you forgot your Mac login password - Apple Support

The translation is - your computer is turned off. Try again in 13 minutes.

It sounds like the poster may be guessing at different passwords. But Linmos and Ingo2711 are correct. You will need the administrator password to turn the Mac on and log out of that account. Or, ask your Ex for the password. You will not be able to use that MacBook until this is resolved.

Перевод - ваш компьютер выключен. Повторите попытку через 13 минут.

Похоже, что плакат может угадывать разные пароли. Но Линмос прав. Вам понадобится пароль администратора, чтобы включить Mac и выйти из этой учетной записи. Или спросите у своего бывшего пароль. Вы не сможете использовать этот MacBook, пока это не будет решено.