Home button EXITS apps, how can I change this?

A

AC Question

Home buttom EXITS apps

I got a Galaxy S4 off ebay. Its in perfect condition, everything works great EXCEPT that the home button exits apps which also creates a problem with screenshots, task manager, s-voice etc. I asked the seller and he (says) he didn't change anything to make this happen.

When in an app, the home botton works like the back button, hit it once nothing happens, hit it twice it exits. Screen shots it will exit the picture as well.

I want it to work like normal, where I can double tap/long hold for task manager/S-voice, and do screen shots