Looking for contact to the previous (German) owners of my car

Guten tag,

A year ago, I’ve bought myself a 1986 Mercedes-Benz W124.

The car used to be a Getman Consulate vehicle in Egypt, and because of that, I’d love to get more information about it’s past… Mainly pictures of the car when it was still used by the original owners (up to 2015)…

I do have the names of the previous owners (A man and his wife) along with an address and a phone number that I got from one of the service receipts… I already tried to contact them this way, but with no luck… The Number and the adress are both 10 years old now afterall…

Do you know if I have any other options to contact the owners or possibly their children as the owners might’ve already passed away? I am from the Czech Republic and don’t know much about the German system in this regard…

The owners lived in Bonn and Dachau

Thank you very much for any tips!