Neighbour regulations

Things are like this, im living in a row house so gardens are pretty close to eachother and as im playing basketbal on regular basis in my garden it happens from time to time my ball falls into my neighbours garden. My neighbours are random retards that buy random builds

random example


So here comes my question, what if my ball falls onto this shit build and it broke down, will I have to pay it or not..

Regulations are different from country to country I guess so some update from someone that living in belgium might be most valuable for my case then ;D