Complex sentence: Hans Knirsch was their leader from 1918 to 1933, when he was succeeded by Konrad Henlein; in 1935 Karl Hermann Frank became the deputy leader of the SdP.
Split into simpler sentences: Hans Knirsch was their leader from 1918 to 1933. Leader of the new SdP was Konrad Henlein; in 1935 Karl Hermann Frank became the deputy leader of the SdP.