None of the Settings tabs work ("My Device", "Accounts") - PLEASE HELP!!

A

AC Question

Hi there,
I have a major problem with my Galaxy S4; the Settings tabs ("My Device", "Accounts", "More") have recently become unresponsive.
Also, the BACK and the MENU buttons do no longer work.
Last weird thing: when horizontally rotated, 2 keys on the Samsung keyboards are unresponsive: "o" and "9" .. !? It's like the area of the screen is damaged but it actually isn't,
I have tried a FACTORY RESET but to no avail.
Any ideas please ?
I'm getting desperate!