It is stated in the traffic rules that if the view is not adequate, reversing or turning around must not be done unless looked after by another person or the driver visually ensures there is no danger or damage.

Furthermore, if the driver's view is inadequate, he must not reverse or turn around except under the guidance of another person or unless the driver himself has made sure that danger or injury cannot arise as a result.

It is therefore not enough to simply open a door and try to get an overview, you must know that you have a sufficient overview of the situation.