I saw this film at the end of 20th century. Young girl to escap from some orphanage has to have a sex with security guard. After that she met some rich man on luxury car (possibly BMW of Merceds cabrio) who loved her. But in several days he told her that he need a girl who will sleep with his rich clients to find out some dirty secrets to blackmail them. She agreed and worked some time such but at the end he murdered her.
Some moments that I remember: man once gifted her mechanical piano to play for clients; the first client was a metallurgical tycoon, he had a bomb in the yard of the plant, which the Americans dropped on the plant during the war, the girl stood near the bomb and the men argued which of them was more dangerous.
I only found this page today, so this reply is waaaay late, but it sounds a lot like Das Mädchen Rosemarie (The Girl Rosemarie)
https://www.imdb.com/title/tt0117132/
There’s also a 1958 version (https://www.imdb.com/title/tt0051963/), if the first one doesn’t quite fit.