Park damage on “sample journey”

Hello! Please for help! I won a voucher for a “experience ride with a BMW” for a weekend of my choice during a competition. I picked up the vehicle from the dealer last weekend. Before that he copied my driver’s license and filled out a sheet with my data (address, tel.nr. etc.). Then there was a short introduction to the automatic circuit etc. Before driving away he still meant I should deal with it carefully, since they realistically high self retention on their vehicles have, although it is of course fully covered. I was a bit stunned, but no longer thought about it as I was looking forward to the new car. I signed or never saw any conditions in case of damage etc. As the devil wanted, a little unhappy happened to me when I parked backwards and I easily tanged a house wall (yes, I know I can hald times) The result were very small paint damage on the rear bumper. Return of the vehicle I reported the damage to an employee who thought the damage had to be looked at carefully and they would then report to me. Nothing further, I drove home. Today the gentleman with whom I had picked up the vehicle came and said I had to pay a deductible of about 1020€ for the replacement of the bumper, because they wanted to sell the car still and therefore the whole part had to be replaced. us? By the way, come from Austria. Thank you in advance for any answer.