I think you have to accept it is defect. Go to a Sony certified repair shop, or when the costs for a repair are to high, but a new one. Sorry, but there is no such thing as a magic spell to cure your camera over the net.
Compact cameras are not ideal for this kind of subject. Depending on the amount of manual control available, set a high ISO, a medium aperture and a slow shutter speed with the camera on a tripod.
Thank you. If this device will accept a memory stick, then the make is immaterial. As for overwriting files, this will only happen if the files have the same name as the ones already on the device. To be sure, rename the ones you wish to copy across before you do so - a simple alpha-numeric character at the end of each file name will do the trick. HTH
Tony
Since you have omitted to inform us as to what the actual equipment is, we cannot answer this question, I'm afraid. May I suggest that you consult the manual.