Complex sentence: Butch and Tom take turns trying to one-up each other and win the affection of Tom's girlfriend by lifting heavier weights than the other, but Butch is unable to lift a heavy barbell.
Split into simpler sentences: Butch and Tom take turns trying to one-up each other and win the heart of Tom's girlfriend by lifting heavier weights than the other. Eventually, Butch is unable to lift a heavy barbell.