I deleted mails from my Gmail account through the inbox Mail app but it is still saved in All Mail folder and it take 7.5 GB storage

Hi Ossi23

We would love to help resolve the issue you're having. If you're deleting a large number of emails, it may be best to log into your account on the web and delete them from your native account to remove them directly. That being said, below we'll include the steps to delete them from the Mail app in iOS. If the mail was somehow saved in your account, you may need to log in there to delete the saved emails.

"Delete multiple emails at once 

1. Open Mail and go to your Inbox.
2. Tap Edit in the upper-right corner, then individually select the emails that you want to delete, or tap Select All. To select multiple emails quickly, swipe down through the checkboxes.
3. Tap Trash or Archive. If you only see Archive, touch and hold Archive to see other options like Trash Selected Messages.

To delete a large number of emails, you might find it easier to use your email provider's website.

Set Trash or Archive as your default option

Depending on the type of email account you have, you might see Archive instead of Trash when you try to delete emails. You can edit where your deleted messages go in your Mail settings:

1. In the Settings app, tap Mail.
2. Tap Accounts.
3. Tap your account.
4. Tap your account once more.
5. Tap Advanced.
6. Select Deleted Mailbox or Archive Mailbox to send discarded messages there.

Swipe to delete and other ways to discard one email

• Swipe left quickly over a single email.
• Touch and hold an email from your Inbox, then tap Trash Message from the menu.
• Tap the Archive button  or the Trash button  from within an email.

You can also use the steps to delete multiple emails to delete a single email."

Reference: Delete emails on your iPhone or iPad - Apple Support

Cheers!

Cheers!