What is the average speed limit around playgrounds

Speed ​​limit in front of playground

Hello, we have a house on the outskirts of the city, it borders on the forest. We have full right of way to the next street (3 KM). We have left this road open anyway, it is used by forest visitors, we also tolerate this. Tonight, around 6:15 p.m., when I came home from work, and drove down the street to our house (always drive really fast on the straight road), it suddenly flashed red, I was flashed. I stopped and reversed. 2 policemen stood next to a mobile flash unit, which they had apparently just installed. I asked: "Are they really flashing here at the moment?". One of the policemen then said: "Yes, due to the high number of cars that want to go to the forest parking lot, many drive too fast here". I asked: "What is the speed limit on MY street? According to the land register, it belongs to us".

I thought the policeman would now apologize, but he said "50 km / h, no speeding here", please leave the scene. I said, "That doesn't exist," and drove home. Now I wanted to ask what it looks like, MAY the police do what they do, and what speed limit should apply on my street, just because it is a "country road", it is private, and there is no "50 km / h" Restriction"?!