1. The only way I have found to easy access your icloud account (where all ohotos are stored and where your iPhone will regulatrly say it’s out of space and try to charge you a lot for getting more space.
2. Once logged in with your apple ID, you can actually click iCloud Photos and see what your phone automaticaly stored in the cloud. You can delete these photos to officially save space, but Apple will keep copies of them forever, of course.
3. Delete all the crap. Now we need to make sure it also disappears from the iPhone device. Because at first glance it seems like nothing was deleted from the phone(!) (Seems it wasn’t syncing because low wifi signal, waiting to see what happens.