Insurance does not recognise expert opinions

Hello together I hope you can help me with a problem that I have with my insurance. About 4 years ago there was a hail damage on my car. According to the expert it was a damage of 4000€. Since I needed the money then, I had the amount paid out without VAT. Since recently some scratches have been added I removed my car with the help of an acquaintance the dents and completely repainted. Then I called my insurance and there The good woman on the phone told me that I should prove an invoice to the workshop. I explained to her that there is no one since I have fixed the damage myself. She told me to send her current pictures of the car, chassis number, etc.. Since I already had a bad feeling during the phone call, that my own pictures are not accepted as proof, I did not get the necessary information. I have sent this report to my insurance company and received a reply yesterday stating that the report is not sufficient and that I have to send a workshop bill.As mentioned above, there is no invoice because it was an own service. Now to my question: Can the insurance company refuse this report? If not, how can I bring the insurance company? Would it be great if someone had a case like this before and could give me tips on how to behave when I call the insurance company on Monday. Is there even any court rulings that I can refer to? I don’t understand the behavior of the insurance company. If I had a workshop bill they would have to pay me the VAT that was retained at the time. Just like in this case they would have to remove the entry in the HIS and would have no or, if at all, only a small cost. Sincerely, I