I want to completely wipe my Samsung Galaxy Tab 4 and install a new android system.

[Android Central Question]

I have a samsung galaxy tab 4, it's storage capacity has been steadily going down. I had apps and pictures and videos, I had to delete all my pictures and videos and most of my apps, it helped very little. The tablet is rooted but I can't find how to delete any superfluous files. I'd like to wipe everything out and install a new OS on my tablet. Unless someone has a better idea.