My submission storage is about to finish. If I delete old entries, could I increase storage?

Keep in mind that deleted submissions are not recoverable. You can check this guide on how to delete submission: https://www.jotform.com/help/377-How-to-Delete-Form-Submission-Data

Yes, you can clear your total submission storage by deleting your submissions. If you want to know more about account usage and limits, please visit this link: https://www.jotform.com/help/408-Understanding-Your-Account-Usage-and-Limits

Let us know if you need further asssistance.