I have a Samsung Galaxy J5 with 16GB internal memory and 32GB SD card. I moved as many apps as I could to the external memory. However, mt internal memory is always used up to at least 15GB, and as soon as it reaches 15.5GB (which is every few days) it starts warning me of dangerously low space. Even if I move all pics, videos, etc to external it still does not free up more than 0.5GB. What do I need to do to get the maximum free space on internal memory?