Internal memory almost full

I’ve got Samsung Galaxy J5 with Marshmallow 6.0.1 and in this phone I’ve got internal memory of 8 gb and a memory card of 8gb. I’ve stored every little picture and audio in external memory and many apps too but the system memory takes up 3.28gb and the apps take 3.83gb and there’s no space left after that. I don’t know what to do I don’t even have many apps and games in this phone. Please help me on how to save up internal memory space without having to move everything to external memory?!!