PayPal is of the largest global payment gateway solutions. They operate in almost every country including Germany. It is easy to use and set up. PayPal has a very powerful API which can be used to customise the payments based on the merchants requirement.
Braintree, a full stack payment platform in Germany charges the lowest transaction fee of 1.9% €0,30 per successful transaction. Braintree charges this transaction fee on credit and debit cards payment. The AmericanPayment Gateways (Germany)