We would understand you are skeptical or if you will..hesitant about the factory reset..if that's the venue you don't wanna take..hear me out:
My mom has a J7..and does exactly what yours does..apparently the internal storage fills up too quickly so the phone starts acting up..freezing, lagging, sometimes reboots, asks for apps to be deleted and so on..
So I rescue her day in a way that turns out to be very effective by..
First you don't just simply clear the apps and users data..you actually manually delete it..
You have to go in the folder(any of your choice..the native is good)..then headed to
The Storage..where every single app you've downloaded hoarders bunch of data..then you go to each one and delete all that junk(make sure you save what you wanna save..then get rid of the rest.
Example..Whatsapp, you go inside through the folder..Media..videos..delete them, images..delete them, and so with the rest that are in there..
Then after that..you go to the phone system..look up strange..and then now you can clear the user and app data that is irrelevant.
I hope this helps.