Complex sentence: He set the course record in 1994 with a time of 2:07:15 before that record was broken 12 years later by one second when Robert Kipkoech Cheruiyot, a fellow Kenyan, won the 2006 race.
Split into simpler sentences: He set the course record in 1994 with a time of 2:07:15. That record stood for 12 years until it was broken by one second when Robert Kipkoech Cheruiyot, a fellow Kenyan, won the 2006 race.