How to see what is stored in System memory area?
Just get X-plore mate ;D. I have been usign it since 2006. It is available on multiple platforms. 


You can see system folders.
You can see hidden files and folders.
Which you can delete/copy/move (be careful when you do that)
You can open many archived files as well.


https://play.google.com/store/apps/details?id=com.lonelycatgames.Xplore