What is the right course of action?

Your choice (1 “I have to wait”) is correct because the motorbike is coming from a road marked with “Do not enter” signs. That means this side road is one-way against that direction, so traffic is not allowed to come out of it toward you. Since the motorbike is there anyway, it is effectively coming from a prohibited direction and cannot claim any right of way.

In German rules, you must still avoid endangering anyone, even if the other road user is in the wrong. So you wait and let the motorbike clear the danger area, then continue. The key rule of thumb for similar questions is: right of way only applies to lawful traffic; if someone appears from a direction where traffic is forbidden, you don’t have to “yield” as a right-of-way rule, but you may have to stop to prevent an accident.