Check your password manager. What other accounts is the e-mail address account linked to? Change it, then delete the account.
If you don't have a password manager: Now is the time to get one. I recommend KeepassXC (PC, cross-platform) / KeepassDX (Android). Combine with Syncthing for cloudless cross-device sync of the password database file.
Also, don't worry too much. You wouldn't be the first to lose access to an e-mail address. Governments or "other important accounts" usually have procedures to deal with that issue. But: a Google account shouldn't be linked to anything important anyway, let alone government accounts.