Accept reviewers?

Evening, last year one of them was scratching my car when I parked out. However, since I could not prove this without witnesses and the other claimed the opposite, I had to report this to his insurance company and he did the same with mine. My insurance now decided on a 50/50 regulation. Thus I would have to pay 50% of his damage, because it would be cheaper for me because of the otherwise threatened upgrade. But now came the request from the opposing insurance company. ng after an appointment to compare the vehicles in front of an expert. This is a lady of the DEKRA. Now I ask myself, should I join this or not or put it on a neutral expert whom I choose myself??? If I refuse this, the opposing insurance will certainly not take over a cent of my damage, right?? Who, by the way, has to pay the expert of the DEKRA, does this end up on my account??? And if I reject this now and who has to pay for it? Would be grateful for many factual answers.