The iPhone Language selection also changes the priority of the App Language.
How can I have the iPhone Language as English and the first priority language for Apps as German, not English?
[Re-Titled by Host]
Assuming you are talking about the language of the menus and dialogues, it's normally not possible to run apps in a different language than that being used by the iOS interface. The only exceptions would be apps that have an independent setting for their language or apps which are not localized for the language of the iOS interface.
How can I have the iPhone Language as English and the first priority language for Apps as German?
