Complex sentence: Berg had taken a semester off during his sophomore year to study improv at ImprovOlympic in Chicago, Illinois, where he learned the Harold, a long-form improv format developed by Del Close and Charna Halpern.
Split into simpler sentences: Berg had taken a semester off of his sophomore year to study improv at ImprovOlympic in Chicago, IL. There he learned the Harold, a longer form developed by improvisers Del Close and Charna Halpern.