bunq is a Dutch bank, so you also have a Dutch IBAN. This starts with "NL" and not with "DE", as is the case for German bank accounts.
The format for a bank transfer is then as follows:
IBAN: NL01BUNQ23456789012
BIC: BUNQNL2A
The BIC is sometimes also given as BUNQNL2AXXX, both work. Please note that the law does not forbid you to transfer money to a foreign bank account. Nevertheless, the Dutch IBAN could perhaps lead to queries in the case of state payments (child benefit, unemployment benefit). With the SEPA reform, however, this payment cannot be refused.