All I can give you is E-class but it might be the same -

Routing diagram would be near the back of owners manual if you have one. Examine area under tensioner pulley. There should be a 17mm hex at about the 7 o'clock position. If so, put a wrench on it and turn counter-clockwise to pivot away from belt and slip it off.

Maybe make a diagram of current routing before taking it off?

Also, check manual for the length of poly-v belt. Some engines have two lengths depending on which options.