Contacts transfer to Benz

Given the fact you state you have 11K contacts, the first thing I would do is ask Mercedes Benz how many contacts their device will handle. I have a 2015 MB and it syncs contacts just fine. If I go on my iPhone to Settings>Bluetooth and tap on the small blue (i) at the end of the line, it opens a page for additional settings for the vehicle and Bluetooth. There is a switch for Show Notifications, Device Type, Sync Contacts, Groups for Contacts, All Contacts, and Forget This device. I, however, only have around 750 contacts. I know that my vehicle before the MB would only sync 500 contacts at first, but that software on the car was updated later and would sync more. I'm not sure of a limit for the MB, however your MB dealer would know that.

Those all appear correct, just like mine. Although I do not have the Device Type set as Speaker. Is it working, or is there still something wrong? If there is still something wrong, what is it? When you say it is not transferring contacts as you hoped, is it transferring at all, or explain what you hope versus what it is doing.