First of all, only a few amount of credit cards will charge you an interest rate, because only revolving credit cards and credit cards with a limit grant you actual credit. Most cards are just debit, prepaid or virtual cards with no limit.
If you want to find out your interest rate, you can check the pricing table from your bank. This can be found under "Preis- und Leistungsverzeichnis", or maybe "Preisübersicht", "Preistabelle", "Kostenübersicht" or similar keywords. Banks cannot hide the interest rate from you.
You should expect an interest rate (APR) at around 13% to 20% per year.