Complex sentence: Gallico's career was launched by an interview with boxer Jack Dempsey in which he asked Dempsey to spar with him, and described how it felt to be knocked out by the heavyweight champion.
Split into simpler sentences: Gallico's career was launched by an interview with boxer Jack Dempsey in which he asked Dempsey to spar with him. Gallico described how it felt to be knocked out by the heavyweight champion.