Car towed, normal procedure?

Hello together, My father was towed, parked at a sidewalk sink. Okay so far as he saw it. So the car bought free at the towing service and drove home. After 2 weeks then the warning came from the city in the amount of 15€ (you have to pay clearly he also made immediately). Now about 6 weeks after that comes another letter from the city of Herne which still has an administrative fee of 50€ to him because of the above mentioned offense. The days still come by post. Is this now normal ? Administrative fee 50€ ? A bit high for three letters that could also be done in one letter?