software update navigation button not working

[andy s5 mini]

On my Samsung Mobile s5 mini the bottom corner touch buttons (back button & I can't think what you call the bottom left corner action button). But they have stopped working after doing the software update anyone know how to get these working or reset the device back to the previous software

 

[B. Diddy]

Welcome to Android Central! Try wiping the cache partition: https://support.t-mobile.com/docs/DOC-10683