Manisha Err, you having a DE IBAN at bunq does not change anything about your payment cards. Card acceptance always depends on the card scheme (for example Mastercard or Maestro, but in Germany there's also the domestic girocard card scheme). If you're at an establishment that only accepts girocard cards, then these kinds of cards will be the only ones that'll work there, unrelated to what kind of bank account you have.
That being said, indeed store clerks or restaurant staff usually have no idea at all about these things, so asking will usually not lead to any fruitful answers. They will say that it'll probably work when it doesn't and also the other way around.
