Complex sentence: Wojtowicz, a former bank teller, had some knowledge of bank operations, however, he had apparently based his plan on scenes from the movie "The Godfather," which he had seen earlier that day.
Split into simpler sentences: Wojtowicz, a former bank teller, had some knowledge of bank operations. However, Wojtowicz had apparently based his plan on scenes from the movie "The Godfather," which he had seen earlier that day.