The CD laser is OK but the DVD laser is dead.

Replace the DVD drive with a new one, or send to VDO Siemens in Germany for repair, or buy another 2nd hand Mk4 nav unit as a replacement.

Given that your car is <4 years old, maybe you can get the unit replaced under warranty from the dealer.

If you replace it yourself, I will consider buying the old Mk4 nav unit, as a source of spare parts.

Jochen