What applies at this junction?

Your answer is correct.

This junction shows a priority regulation that applies to a bicycle priority road, as indicated by the blue sign with a bicycle and the word "Fahrradstraße" (bicycle street). The red surface with bike symbols and the "Yield" (give way) sign on your side indicate that you must yield to cyclists traveling on the bicycle street.

Since you want to cross the junction straight ahead, you must give way to cyclists on the bicycle street. However, since no cyclists are currently blocking your path and you are already positioned at the yield line, you may proceed straight across the junction when safe.

Turning right or left was not the issue here; the main rule is to always yield to the bicycle priority road users before crossing. Your option to cross straight ahead is allowed once the way is clear.

In summary, at this junction you must give priority to bicycles on the bicycle street, then you may safely cross the junction straight ahead. This is why option 1 is correct.