How can I change from app store Germany to App Store Spain Trying to download Pokerstars.es, but I always get German App Store and in Spain Pokerstars.eu can not be played.
go to Setting and choose "iTunes Store and App Store" 
Tap your
Apple ID and in the popup that appears tap "View Apple ID"
Insert your password
Tap Country/Region and again Contry/Region (if you have an active subscription as Apple Music, you cannot change the Country)
Choose the country from the list, and complete all the form that appears.
When you'll finish, you can use the Stores from that country.


P.S.
All your purchased are related to the country where you bought them, so you won't find any purchase in the dedicated section, when you'll come back to your country, you'll find all your purchases.

here's the official article Change your iTunes Store country or region