How to delete hidden files consuming internal memory in Android?

I have 16gb internal memory in my Android phone (Asus Zenfone 5). I am using only around 3gb of memory and rest is being consumed by some hidden files. I am facing problem of memory shortage (only around 100mb left). I figured out there are two large files in DCIM folder of around 4.6GB in .thumbnails folder naming .thumbdata3xxxxxxxx . I deleted these files but the memory usage is still not reduced. Are these files not deleted? How and where can I search for the hidden files consuming internal memory? Thanks