stuck on deleting a gmail account

If you only want it off your phone rather than gone forever, don't delete anything. Remove the account in the accounts section of the phone's settings instead. Everything stays and you can add it back later.

It isn't in the Gmail app at all any more, which is why it looks like it vanished. Go into your Google Account settings, Data and privacy, then scroll right to the bottom - there's a delete a Google service option and separately a delete your whole account one. The first keeps the account and only kills Gmail, but it makes you add another address to sign in with first, so have one ready. Run a Takeout export before you press anything. The address is gone for good afterwards, you can't re-register it later.