I tried that. Exactly I restored the phone in iTunes yesterday, but not in DFU mode. It should helps? Thanks for the reply!

I bought a second hand iPhone 4. It is in a very good cosmetic condition but there are some problem with the hardware: the camera doesn't work (shutter won't open) and the mute switcher does not work, too. And it's not over. When the phone is ringing or I'm playing with any game there's no...