What must you watch out for now?

Your answer is fully correct. When stopped at a red traffic light and about to proceed, you must pay attention to both the vehicle directly ahead and any bicycles approaching, especially from behind or alongside. According to German traffic rules, you need to ensure the vehicle in front moves safely and watch for cyclists because they are more vulnerable road users and may be in your blind spots or on the side. While motorbikes are also important to watch, in this specific situation, the focus is on the vehicle ahead and the bicycle because they pose the most immediate interaction risks as you start moving. This attention helps prevent accidents and ensures safe merging into traffic after waiting at a red light.