Who is the cause of the accident?

Hello, my wife had a small accident today. According to the officials, it is not quite clear who the cause of the accident is. My wife was driving behind a driving school car that was very slow (feeled 20km/h at 50km/h registered). She could see very far straight ahead, there was no oncoming traffic or a danger to other road users and she decided to overtake the driving school car. My wife was ready that you could almost slip into your lane again. e, when from an exit on the left side (there is a yard of a shop where there are several parking lots) a vehicle drove in as far as there was a collision. Our vehicle was ground from the middle of the driver’s door to the rear wheelwheel. In the opposing vehicle the front bumper is sanded left. Unfortunately, the statements of the officials do not indicate who is now cause of the accident. First, the officials should have said that it looks like this, As if my wife was the cause of the accident. After that, they should have said that it is not prohibited to overtake this route and that it is understandable because a slow driving school car was on the way. Then the officials should have said that the opponent’s vehicle should not have been allowed to enter the road as long as one is not sure whether it is free. These are all contradictory statements of the officials, where I simply cannot understand, Who is the cause of the accident? What is your opinion on this? I have reported it to my insurance company, they have taken everything and said that I should call the opposing insurance company so that they can regulate the damage. So they seem to assume that the opponent is to blame for the accident. Isn’t that possible only when it is clear who is the cause of the accident? So I can’t just have an expert report and an expert report drawn up now, where there is still an accident. I don’t know who is the cause of the accident. Who will then cover these costs? I just don’t know how to proceed at the moment thanks