How to properly regulate parking ramps with opened door We are victims and ask for help.

It’s about someone who hit my mother’s door in the car in a parking lot on Saturday and created a macke. (I can’t take care of it until today) On the subject as My mother told me on the phone. On Saturday, a man knocked out the door in the car carelessly as she got off and she was lucky that she was standing near and heard this. After some discussion, the Lord has urged his son to join us. How does the other insurance company get in touch with her? Or should she now go to a workshop (expert) and make an estimate? Or should you settle it outside of the insurance company (is this still possible) if my opinion is fictive invoicing best. (car is 8 years) so call the creator? PS like long it takes for the opposing insurance to register? dear greetings to all