Complex sentence: He taught astronomy and geodesy from 1920 to 1928 at the University of Neuchâtel and then in 1928 became a professor at the University of Lausanne, where he retained his academic position until his unexpected death from a heart attack in 1936.
Split into simpler sentences: He taught astronomy and geodesy from 1920 to 1928 at the University of Neuchâtel. In 1928 he became a professor at the University of Lausanne, where he retained his academic position until his unexpected death from a heart attack in 1936.