Complex sentence: She is approached by a man, Hans Beckert (Peter Lorre), who is whistling "In the Hall of the Mountain King" by Edvard Grieg, and he offers to buy her a balloon from a blind man.
Split into simpler sentences: She is approached by a man, Hans Beckert (Peter Lorre), who is whistling "In the Hall of the Mountain King" by Edvard Grieg. He offers to buy her a balloon from a blind man.