Leon There's no problem with insta payment. Or if there is, it's not applicable here. The Sparkassen in Germany support SCT Inst, but they don't use it by default. For nearly all of them it's an extra service that the sender of the payment has to pay for, and if they don't, the payment will be sent as a regular SEPA credit transfer.
That's why it's not unusual that @Jens 's payment hasn't arrived yet. Depending on what time of day yesterday his wages were transferred, the Sparkasse might've not been processed it until now and it could even take until tomorrow for the money to arrive.
Of course, bunq could also have problems. But I already received a transfer from ING Germany that was made yesterday, so seems to be working fine as far as I can tell.