why is my lumia 435's search home and back button not working?

I upgraded my Lumia 435 to windows 10. I'm not sure if its the update or my hardware that is giving me problems. but to my best of knowledge I think its the update that caused the problem because it was not giving me any trouble. I would like to know if I must send it in for repairs or is their a another way to troubleshoot this problem. I've already tried the hard reset and it doesn't work. please help

from Windows Central Forums http://ift.tt/2ehiwlH
via IFTTT