How do I get back the photos permanently deleted

Were you backing them up? Or were you syncing them with iCloud? You cannot be doing both. If you were syncing them, once you delete them permanently, they are gone.

If you were actually backing them up, you can restore the phone from iCloud:

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Note that doing this will overwrite everything currently on the phone.

Have you backed up your iPhone previously to either a computer or iCloud?

If not then permanent is permanent.

Then you should be able to restore the photos and videos to your iPhone. I can't tell you how as I don't use iCloud so have no first hand experience with it. Do a Google search for something like "restore iPhone from iCloud backup".