Chosen Solution
So essentially I got a Z3 for pretty cheap (200 Euro) however the camera lens is full of dirt which makes the photos come out kind of bad. I was wondering if I could remove the back cover, clean the lens and use new back cover adhesive but keep the same glass cover?
Absolutely! Just be careful not to damage when removing. It is adhered to the back of the phone and cracks easily. I would use plenty of heat and have plenty of patience when removing the back. I would also check ifixit for a guide, or youtube!
I would recommend replacing the entire back glass after removing it. They are dirt cheap to buy and saves cleaning it/adding new adhesive. You can probably buy the back glass with adhesive not much more then the actual adhesive.
