I'm not familiar with German laws regarding bike lights, so am hesitant to suggest any battery-operated lights; will leave that to others with more knowledge. However, I will say that for your price limit, you could get a decent setup built on a Shimano dyno hub. Your commute is about the same length as mine, which is rather short...But I still end up screwing around with recharging lights more often that I would like. With a dyno setup, you will always have light.