Hi Patrick.
Please note first that this community is English only.
We support for now credit card only for Wappler subscriptions.
But you can just get a virtual online prepaid credit card, there are many services that offer that also in Germany like:
https://www.mycard2go.com/ (Germany)
https://pay2d.nl (The Netherlands)
So just signup with such a service, transfer some money to your virtual credit card with your normal IBAN transfer and you can pay for the Wappler subscription with it.
Do make sure that there is enough money to renew the subscription on the period you choose otherwise it will be quickly cancelled.