iPhone users can change the communication language for Siri using the General Options. If you want to speak with Siri in your native language then you can try this option. iOS 7 currently supports 19 languages like Chinese, English, French, German, Italian, Japanese, Korean, Spanish etc. Given below are steps for changing Siri language from English (United States) to German (Germany).
Step 1: Tap the Settings icon on iPhone home screen.
Step 2: Navigate to General Options in the Settings screen.
Step 3: Tap Siri under General Settings screen.
Step 4: In Siri screen, navigate to Language option. This should list all the available languages for Siri.
Step 5: Now to change the language, pick German from the language list.