Black metal sign with a green arrow: This is how you behave correctly
When approaching an intersection where there is a sign with a green arrow next to the red light, act like you are at a stop sign before turning right and park your vehicle in front of the light completely at a standstill. Only as soon as your vehicle has come to a standstill and you have checked whether the road is clear can you turn right despite the red traffic light.
If the traffic light is green, the sign with the green arrow has no meaning, since the signal from the traffic light opens the road anyway.
There is no obligation to actually turn at this traffic sign. If you feel unsafe or can’t see the traffic fully, just wait for the traffic light to turn green.
Other road users who are standing in front of you at such an intersection despite the sign with a green arrow should not harass you with their horns or lights.
Danger: If you turn off without stopping at the intersection beforehand, you can face a fine of between 70 and 150 euros and a point in Flensburg.
Caution, risk of confusion: the green glowing arrow
The green tin arrow should not be confused with the green arrow as a traffic light signal. The main difference is that you can turn directly at the intersection without stopping when the green arrow is lit. If this does not light up, you have to pay attention to the normal traffic light signal and wait.
Unlike the green tin arrow, you really have to turn with this signal.
You can read more about this topic and where the green sheet metal arrow comes from here from the colleagues at EFAHRER.com.