Once you hit 100% of your quota, your forms will go into Private Mode (no new responses can be collected).
Forms will automatically collect response again when:
Your monthly cycle resets, or
You upgrade to a higher plan.
Deleting submissions is not an option and will not free up extra submissions
for that month. Once a submission is counted, it stays in the monthly total.
Pro Tip: If you expect a sudden spike in submissions, consider upgrading in
advance so your forms don’t stop collecting.