Complex sentence: Berggrav also became involved with the "Østlandsk reisning" political party and the Østlandsk ungdomsfylking youth movement with Alf Frydenberg--both social movements sought to incorporate the language spoken in eastern Norway into the national written language.
Split into simpler sentences: Berggrav also became involved with the "Østlandsk reisning" political party and the "Østlandsk ungdomsfylking" youth movement with Alf Frydenberg. Both social movements sought to incorporate the language spoken in eastern Norway into the national written language.