Complex sentence: While still a student he joined the Social Democratic Party ("Sozialdemokratische Partei Deutschlands"/SPD), and between 1910 and 1920 he served as a Berlin city councillor.
Split into simpler sentences: While still a student he joined the Social Democratic Party ("Sozialdemokratische Partei Deutschlands"/SPD). Between 1910 and 1920 he served as a Berlin city councillor.