Complex sentence: He won gold at the 2017 World Championships in the 400 m hurdles, the first gold medal at the World Championships for Norway since 2009 and the first in a track event since 1987.
Split into simpler sentences: He won gold at the 2017 World Championships in the 400 m hurdles. This was Norway's first gold medal at the World Championships since 2009 and their first in a track event at the World Championships since 1987.