Complex sentence: Bob Saginowski (Tom Hardy) is a bartender at a neighborhood bar in Brooklyn called Cousin Marv's (James Gandolfini), which operates as a "The Drop" bar where criminals launder money.
Split into simpler sentences: Bob Saginowski (Tom Hardy) is a bartender at neighborhood bar in Brooklyn called Cousin Marv's. Run by the eponymous Marv (James Gandolfini), who is Bob's cousin, the bar operates as a "drop" bar where criminals launder money.