This Time it Must Be Caviar(1961)

Original title: Diesmal muß es Kaviar sein

Thomas Lieven is a German secret agent trying to leave that profession, to live a peaceful life. Adventure is too strong an appeal, he starts working again, and soon it's difficult to say if he is doing his job, or turned out as double agent for England, France or even communist Russia! To save his skin, he'll do - almost - anything, to anyone...