Complex sentence: John "Lucky" Garnett (Fred Astaire) is a gambler and dancer who, after showing up late for his wedding to Margaret (Betty Furness), is told by her father that he must earn $25,000 in order to demonstrate his good intentions.
Split into simpler sentences: John "Lucky" Garnett (Fred Astaire) is a gambler and dancer. Margret's father tells Lucky that he must earn $25,000 in order to demonstrate his good intentions.