Complex sentence: When he was 17, he joined a Jesuit school in Vienna and following his graduation he became a school instructor (chiefly of mathematics and physics) in Vienna, Graz, Neusohl, Gorz, Laibach (Ljubljana), and from 1764 Klagenfurt.
Split into simpler sentences: When he was 17, he joined a Jesuit school in Vienna. Following his graduation, he became a school instructor (chiefly of mathematics and physics) in Vienna, Graz, Neusohl, Gorz, Laibach (Ljubljana), and from 1764 Klagenfurt.