Complex sentence: Rueffer went on to marry a bank director named Schmidt, but he had drowned in his bath during a visit to Berlin, so when Brauchitsch returned from East Prussia in 1937, the pair resumed their affair.
Split into simpler sentences: Rueffer went on to marry a bank director named Schmidt, but drowned in his bath during a visit to Berlin. So, when Brauchitsch returned from East Prussia in 1937, the pair resumed their affair.