Complex sentence: George visits a friend, Deena, and her dad, "Pop," who had a mental breakdown, starts tinkering with George's car's engine and smashes it with a tool out of frustration.
Split into simpler sentences: George visits a friend, Deena, and her father, "Pop," who had a mental breakdown. Pop starts tinkering with George's car's engine and smashes it with a tool out of frustration.