wifi problems it turns on and off all the time

Do you mean the wireless signal drops off intermittently or the wireless button keeps going to off on the phone? Usually this can be fixed by retightening the screw located at the top of the phone when you take the back cover off.

You'll have to take the two pentalobe screws located at the bottom of the phone then push the back cover North of the phone to unlock it for you to be able to life the back cover off the iPhone 4s

After you get the back cover off. Use a Phillips head screw driver to loosen then tighten on all the metal plates that have a screw to hold it in. Do not tighten very hard as this is not required and can cause issues if over tightened alot.