KONSTANTINOS-Magenta-Quokka There are two types of cards in summary:
The amount of the purchase is immediately debited from your account.
If you don't have the money you can't pay.
The bank authorizes you a certain amount of credit. You make your purchases and the total is debited from your account at once.
Regarding online / offline:
Some terminals are not connected to the internet and therefore do not ask for authorization. This is the case for tolls to go faster.
The Bunq card is a mixture of these two cards.
If you do not have the money, you cannot buy, except, and only in this case, if the terminal is offline.
In this case Bunq accepts the transaction in a maximum of 250 €.
So it's not a real credit card, but an improved debit card.