If you like museums, get the Museum Pass, which grants you access to 30 museums over the course of 3 days. Just a heads up that some of the museums (especially the ones on Museum Island) are so popular you have to book a reservation the day before. Only 2-4 hours of free time per day is quite limiting, though.
Pergamonmuseum is the most popular museum in Berlin, but I believe it’s under renovation work right now (which sucks; it has the best collection of hot naked muscular statues and reliefs). My personal recommendations are Altes Museum, Bode-Museum, the Gemäldegalerie, and the German Spy Museum.
Rüyam Gemüse Kebab makes my favourite döner kebabs. I got addicted to the one on Hauptstraße back when I was there. Other people have different favourite döner stores, so try them all out while you can!
No. Look, it’s reference; as long as it’s reference and not a study or copy, no one should care. In the same way that if you pose a 3D model that someone else made, rendered it out, and used that as reference, you don’t have to mention it.