Memory problem

Friends, few months back i bought this iball's Q27 4G tablet with 2GB RAM ,16 GB internal memory , MARSHMALLOW 6.0. but sooner i discovered that the internal memory was getting occupied too fast than my expectations. But to my surprise, i wasn't able to see wherein the space was getting occupied. Later i tried installing various software's as well as to find the problem but failed in doing so. Afterwards i found out that factory resetting was the only solution to it. But a software like ES File Explorer also wasn't able to free the occupied space of the internal memory, nor was able to show the exact location of occupied space. If anyone could give me a perfect fit solution to this problem of mine, it will be a great help for me.