Invoicing comprehensive damage so right?

The following problem: Self-inflicted accident, car not ready to drive, car has VOLLKASKO. Own insurance sends reviewers. Reviewer issues the following numbers: Replacement value: 20,000 € Repair costs: 15,000 € Remaining value: 10,000 € Insurance wants to calculate as follows: Replacement value 20,000 € minus residual value 10,000 € equals payout 10,000 €. 3 questions about this: 1. Do I have no right to pay out the estimated repair costs, i.e. after fictitious billing? 2. Does this acr method of calculation only if I sold the car as an accident? 3. If I had the car repaired (favourably) and the insurance would prove the repair, would I be entitled to pay the (fictitious) repair costs?