They have replied to the chargeback saying I should request a chargeback with the merchant. I replied citing Mastercard Chargeback rules and give them 2 weeks to do it before I complain to BaFin. So let's wait 2 weeks and then I will complaint.
I am annoyed as this is the first chargeback or even customer service I request of TF Bank and it seems they are not worth their reputation (it is often cited as the best CC in Germany). I am also annoyed with myself because I know about DCC. But I did not encounter it in the last few years (a few ATMs here and there but not any restaurants or shops even when paying contactless) so I had my guard down.