DJ XXL

I have a W204 Mercedes Avantgarde late 2007 but the sytem and the navigation is in german.Now when i try to go to the system and to change it to english cause i don't know german it comes up to my small navigator that i need a dvd to do that.Does anyone knows what should i do cause a uk shop that i contact yesterday said to me that i don't need a dvd infact my mercedes dealer in my country said that i need it but it cost a little bit.
Please a little help

Doa

you have the APS 50 so yes you need the dvd every time you want to use the navigation.