Complex sentence: The Regionalliga Süd was the second-highest level of the German football league system in the south of Germany from 1963 until the formation of the 2nd Bundesliga in 1974.
Split into simpler sentences: The Regionalliga Süd was the second-highest level of the German football league system. It existed in the south of Germany from 1963 until the formation of the 2nd Bundesliga in 1974.