I bought an USB Adapter which emulates a CD Charger. The port wasn't used yet. When I plugged my battery the Radio worked, but I couldn't find the CD charger /USB in my radio source menu. Do I have to code the Radio? If yes which tool and codes do I need? Thank you!
According to installation instructions for a cd changer retrofit on an E90 linked here, yes you will need to code the car for it.
Coding the car will require an INPA OBD2 cable (purchased on Amazon, eBay, etc.) and the appropriate BMW progman software. Some INPA cables will come with software, but it's usually best to get the latest versions. If you have a Windows XP laptop laying around that's the best platform to install the progman/ediabas/INPA software bundle, which also enables fun things like checking trouble codes, inspecting sensor outputs and registering a new battery.
WARNING: Be extremely careful if you choose to code your car yourself! It is entirely possible to "brick" your car. Find instructions on coding through the E90 forums or this link and follow them to the letter. If any of this concerns you, please contact your nearest dealer to get the car coded appropriately.
The problem here is that I have a Professional radio with MOST interface. To adapt an USB interface, you have to buy an adapter which also has MOST. Such an adapter is e.g. the Dension Gateway 500, see this link: Dension E90 Professional (without Navi) pre-facelift. These devices are much more expensive as the adapters without MOST interface (>300 €)