Dear Mr. Franczak,
Unfortunately, there is no news in your case. We presume that the relative of Mr. Erpf does not want to get in contact. I am really sorry. A final possibility on our part would be publishing an advertisement on our website about this case in the hope that somebody, who knows about your father would come forward. Our website is: www.tracing.hu
It has a page for tracing advertisments:
Please advise us if you wish this, and we would do it with pleasure.