I can't delete files I have an issue with my phone, the phone doesn't delete files.  When I delete a file for example a 1 gig file or a game with that same size, the file is gone in the file manager, but the space on my phone doesn't change.

My storage space WAS 1 Gig, and after I delete a 1 Gig file, the storage space should be 2 Gig, but it ends up still being 1 Gig.  

I tried to do a factory reset, and also tried to upgrade my phone to Marshmallow, but the problem is still there.  (Note: My phone is rooted)
I haven't got a rooted phone but the only solution I can give to you is to delete the files from the system applications.

I.e. instead of from the file Explorer, delete photos from the gallery app. And apps from the application manager.