Insurance Accident Opponent Expresses Impairment

Hello, my senior had an accident. In the traffic jam a car hit him on his standing T5. Damage height ~500€. The T5 is Bj 2014 and has 14TKM – replacement value according to expert opinion ~53000€. The expert (self commissioned) has set an impairment value of 170€. The gegerische insurance agrees with the damage amount, but sees the impairment value only at 600€. Can the insurance simply determine this? I have advised my father now once the Call the evaluator and tell him that the VS does not see 170€ but 600€ and what he would think about it. What do you think? Does the opposing VS have to pay for the impairment? My father does not want to commission an RA. sl Letar