Hi,
As far as I can see it displays the German translation on the checkout for your custom field.
On your screenshot, I can see that you're editing the address in the backend and that the interface is in English.
So if you're wondering why you see the values of that dropdown in English while your website backend is in English, then I can only say that it's normal. The system displays the values of the dropdown based on the current language. If you log on your backend in German you should see German values in that dropdown.