Is this about the Apple TV app on your iPad, or on a different streaming device?
Are you in Germany, with a German Apple ID account? Content may be offered in one or more languages, and with zero or more subtitles. How it is offered may be different by title and by country, as determined by the supplying studios. (I don’t expect much German content to have English support, as mass appeal by Germans is generally so averse to other languages in broadcasting.)
Devices have a system language, a preferred audio language, and a preferred subtitle language. All different settings.
Content can only align with that, if available in the stream.