Complex sentence: Its headquarters was located at the party seat of the NSDAP in Munich, but the Planning Department was moved to Berlin in 1936, to improve co-operation with the Colonial Section of the Foreign Office.
Split into simpler sentences: Its headquarters was located at the National party seat of the NSDAP in Munich, although the Planning Department was moved to Berlin in 1936. The reason for this was to improve co-operation with the Colonial Section of the Foreign Office.