Race in 50 Multiplayer events on Nurburgring.
You need to complete 50 Multiplayer events on any of the Nurburgring tracks. The quickest approach is to create a private lobby in the Multiplayer Menu by press and then press to change the options. Set the type to "Timed" and duration to "0:30." With the loading screens, this will take about an hour to complete 50 events. You do not need to win, get a medal, or even have anyone else in the lobby with you. The "multiplayer" merely refers to launching the races from the Multiplayer menu.
You may want to use a car from a German manufacturer to help add a few miles to "The German Connection" requirements.
You can do this using Private Multiplayer by inviting no friends, but adding at least 1 Drivatar to the lobby. Basically the same method as the Long Beach achievements. Otherwise, start a Private Lobby, invite a bunch of friends and do this achievement together. I would suggest using high class cars to minimize the time spent on track towards the achievement.