If you are talking about https://gsuite.google.com
Learn more I hope to answer later, but You did a very safe thing to those that use the domain email unknown person. The risks are very large, and the sooner You do, the better.
Get mail on email@example.com the main sites where you registered and change your mail, just make a new post to firstname.lastname@example.org picked up the mail using pop3 with the old.
In another case, as far as I remember in Google you can register with your third-party email, for example email@example.com and to use the services of Google, in this case, you just need to create your mail in the current account, and then set to retrieve mail via pop3 with my old email