Why does my Tab 4 lag/stutter?

[AC Question]

I bought a Tab 4 on Ebay. It's certainly not a high end device but it seems to be having issues doing basic processing like browsing. I open firefox, it takes a little bit to load, and then the screen flows very poorly. I would describe it as a choppy lag. It's pretty annoying. I'm assuming it has to do with low CPU power and the fact that I did the updates. Any advice or tricks for making it flow better. I'm considering selling it if I can't get it to work a bit better.

Also, I just noticed that the home button feels a little loose... Is that how it's supposed to be or is it wear and tear?