My photos won’t delete off my iPhone.

Ok so, I’m planning to get a new iPhone but I don’t want to lose all my photos because I’ve had this phone for 6 years. However, I have an unnecessary amount of photos because I became a photo hoarder unintentionally but I’m trying to clear up space now..especially considering I’m getting a new iPhone soon, so I’ve been trying to delete a lot of pictures that I don’t want or unnecessary screen shots etc before I get my new iPhone.. but the problem is every time I delete a photo it still appears back into my gallery and I don’t understand why … it wasn’t doing that before? I just want to delete them permanently but it won’t let me. Also, I have 5,300 photos in my recently deleted, but every time I try to delete those permanently as well… they still appear there.. can someone tell me why this is happening or how to fix this? And no my iCloud photos thing is NOT turned on… I did try to turn it on since I’m about to get my new iPhone, but it said I can’t because I need more space… so I don’t understand why won’t my pictures will not delete and keep coming back… it’s frustrating and I really need help…