Help with 2011 Mercedes C300?

Hey y'all! So I have a 2011 C300 that the dealership gave to me while mine is being fixed. I'm going to have it for a week, so I've been trying to learn some of the best features. On the window sticker, it says that it has "Navi+4". Now, how do I use this? And also, I cannot get my iPhone music to play for anything! I've used the iPod connector, USB Connector as well as the standard AUX cord. All help will be greatly appreciated:)! Thanks so much!