Complex sentence: Brüning supported his party's determined opposition to his successor, Franz von Papen, and also of re-establishing a working parliament by cooperation with the National Socialists, negotiating with Gregor Strasser.
Split into simpler sentences: Brüning supported his party's determined opposition to his successor, Franz von Papen. He also supported re-establishing a working parliament by cooperating with the National Socialists, negotiating with Gregor Strasser.