"Back Button" arrow on main screen

For the last week or so I have lost the "Back Button" arrow from the main screen. I am able to open an app, for example, but when I am done or need to go back on the previous screen or to the main screen there is no back arrow lit up. I can only restart the phone to get back to the main screen.

It is the two lighted "buttons" that are on either side of the center button. The center button also does not work. You almost always have to hold down the power button to restart the whole phone. I have also noticed an "uncontrollable" on and off of the phone. When you push the side button to darken the screen, it then uncontrollably will come on and go off buy itself. Unless you turn off the phone