Mr.
I Changed Russian Apple store on my iPad Air in to German , how to change it back?
iPad Air, iOS 8.3
Follow this procedure:
1. Go to Settings > iTunes & App Stores > Apple ID.
2. Tap your Apple ID.
3. Tap View Apple ID.
4. Enter your password.
5. Go to Country/Region in the popup window to change to the desired store.
See also: http://support.apple.com/kb/HT1311