Deleting emails from your Gmail account is final — they’re lost forever once you empty your trash folder. If you want to hide emails, rather than delete them, you can archive the messages instead. This allows you to find and retrieve the emails at a later date.
When your Gmail gets crowded with emails, you can delete the oldest ones, but you won t be able to review them in the future if needed. Archiving old emails is perhaps the best thing to do because you can