thanks for your reply.
I found on Czernowitz.geneasearch.net the reference to the Cz marriage record. I never found the original. According to this site David Hersch Marczak was "aus Bojan, Hauseigenthümer Nr. 514, Sohn des Nachman von Chotin in Beßarabien u. der Gitel". That is all I know.
Do you know whether Nachman is a surname or a given name? And if it's a surname, why has his son an other name (=Marczak)?
I'll take a look at the Family Finder!
Thanks for helping me.