What is the right course of action now?

In this situation, the correct action is to perform an emergency stop because it indicates a sudden and unexpected hazard where immediate stopping is necessary to prevent an accident. Passing quickly through the junction or braking only slightly would not provide enough time or space to react safely to a potential danger, such as another vehicle or pedestrian entering the intersection unexpectedly.

According to German traffic rules, you must always adjust your speed and driving behavior to the situation and potential hazards ahead. If there is a risk of collision or the road conditions suddenly require it, performing an emergency stop is the safest way to avoid an accident. This rule helps protect both yourself and other road users. In contrast, "passing quickly" through an intersection or "braking slightly" can be dangerous if the hazard requires more decisive action.