Damn, it is just on the website? so on the Apple TV is it german by default??
Usually Netflix on Apple TV (or on Rokus) does NOT have a specific language setting, it uses the language setting of the main device.
So you should define English as the language of your German Apple TV, and the German Netflix should automatically stream in English (of course, if the said show is available in Germany with the original track).
I haven't tried, but that's usually the way it works on TV Streaming devices.
I admit this isn't practical for many European users.
Say you want to watch an original US series in English, and then a German film in German instead of dubbed in English... you need to go back to the main Apple TV menu and change the language again.
The whole system is thought out for people who only understand one language...somebody needs to tell our US friends that even *their* brains can handle more ;-)