Complex sentence: For over forty years it served as the seat of both constitutional bodies, the Bundeshaus was expanded and renovated numerous times until these institutions were transferred to Berlin after the Hauptstadtbeschluss (Capital Resolution) in 1999, nine years after the German reunification.
Split into simpler sentences: For over forty years it served as the seat of both constitutional bodies. The Bundeshaus was expanded and renovated numerous times until these institutions were transferred to Berlin after the Hauptstadtbeschluss (Capital Resolution) in 1999, nine years after the German reunification.