Original: In 1981 he was elected vice president of the Bundestag (1979-1981) and then Governing Mayor (Regierender Bürgermeister) of West Berlin (1981-1984).
Simplified: He was elected vice president of the Bundestag 1979-1981, but did not stand for re-election, because he became the Governing Mayor of West Berlin (1981-1984).