You want to drive straight ahead. What should you do if the [red] truck immediately drives off on “green”?

You answered correctly. In this situation, when the light turns green, you must first allow the red truck to move off before you go straight ahead if the truck starts first. This is important because large vehicles like trucks need more space and time to get going, and trying to overtake or drive off immediately could be dangerous. If needed, you may give a warning signal to avoid misunderstandings or to alert the truck driver. You should not drive off at the same time as the truck, because it can lead to conflicts or accidents. Remember: always give priority to larger vehicles starting slowly and use signals for safety if necessary. This will help you handle similar situations safely and in compliance with German traffic rules.