What happens when you press continue on «you are about to unlink your account. When you do this action, it cannot be undone»
Device unlinking logs you out. If you want to be able to log back in again, you either need to link the PIMD account to an ATA account or a Facebook account.
It will log you out of your device so you have to log in with an ATA account or Facebook, if you made sure to link your account with one of those. If not, you have to recover your account.
As previously said, you have to link your account first. If your account is properly linked to ata (with a Gmail) or Facebook, nothing happens. You can login again using the mail and password or your Facebook. Beware that if you create a new account, you need to wait 24 hours to delink it (unless this was changed lately).