Might be time to rip the bandage off and upgrade the phone, I honestly wonder how old you phone is because 64gb for modern phones is really low storage.

9

Clear app caches too. Especially safari/web browser

7

when i upgraded my icloud storage i noticed it got rid of a lot, but not sure if those two things are related

6

you can backup your personal data and then factory reset your phone but that's a huge pain in the ass

2

I had to log into my iCloud mail in my computer and manually delete. Also go into recently deleted folder and delete them

2