Basically the same as anywhere else. You can pay directly with a visa or other charge card, but you will pay more than if you have signed up for an app and pay through your bank account. I have two charge cards one from EWE GO which is a local energy company from my local area and one from ADAC which is the equivalent of the UK's AA and is run in conjunction with the energy provider ENBW which gives me a 10 cent/Kwh reduction on their own chargers and access to 400,000 chargers across Europe including Ionity and Shell Recharge.
You can also use the Ionity network by simply downloading the app (Apple or Android). The latest information from Ionity in Germany:- 496 high power chargers in 110 locations with another 10 under construction.
You could also sign up with Shell Recharge with app and/or RFID card and get access to their sites and partners across Europe. Hope that helps.
Shell Recharge EV Fast Charging Stations | Shell Recharge
MAP & STATUS