On which page of the shop can I configure the url so that customer gets directed to a german payPal payment page ( paypal.de) instead of the english paypal.com?

I am sorry but that is not a variable in our software.

All shopping carts that use Paypal take users to the PayPal.com site. The com site then analyses the payee's address and uses a two digit code appended onto the end of the com address. If you are based in Germany and have your profile set up in German, I would have thought that the PayPal screen would have also been presented in German? If it isn't, I would suggest contacting PayPal customer support to see if it can be resolved through your console.