Reduction in settlement according to expert opinion

I just want to document the progress of my case here, in order to give others possibly an increase in experience: 1. I was damaged on 16.12.. Someone drove me backwards with a 10m long lobster into the rear side when turning. 2. On 19.12. I had an expert report from the DEKRA done. After this damage was a total of 4,765.96 Euro (net). I informed the insurance that I want to have calculated according to expert report. 3. On 27.12. I gave the car to “Karoseriekün costs 800 € plus 117 € for an A6 taillight via Ebay (at Audi approx. 300 €). 4. On 05.01. I received an advance payment of 3000 € from the Allianz after call with the indication that the examination of the GA is still running. 5. On 17.01. I received a final transfer of 555 Euro. The reason for the deduction was “average work costs” to be applied and a painting measure that might not be necessary. 6. On 18.01. I called the insurance company and asked to pay the missing €1200, as otherwise I would sue. I should call again next Monday because the relevant clerk would then be back in the house. She should then tell me how the alliance would still show kindness. 7. I can already make an appointment with the lawyer for Monday if necessary, should I not be satisfied with the offer of the alliance.