You can not directly delete all more than 100 emails at a time. You must have to know how to delete old emails in gmail in bulk. If you know the steps than you can easily delete 100 emails at a time:
Step 1: Click on search option and type older_than:1 y
Step 2: Select all searched emails.
Step 3: After clicking checkbox click on delete
Step 4: Confirm
Step 5: Ok
For more visit: https://emailspedia.com/how-to-delete-old-emails-in-gmail/