Complex sentence: Schumann worked closely with Otto Neurath at the "Deutsches Kriegswirtschaftsmuseum" (German Museum of War Economy) in Leipzig and went with him to Bavaria, when Neurath was appointed President of the Central Economic Administration for the Bavarian Soviet Republic.
Split into simpler sentences: Schumann worked closely with Otto Neurath at the "Deutsches Kriegswirtschaftsmuseum" (German Museum of War Economy) in Leipzig. All three subsequently went to Bavaria, where Neurath was appointed President of the Central Economic Administration for the Bavarian Soviet Republic.