Complex sentence: In the 2016 Olympic Games in the men's 400m he won the gold medal with a World Record time of 43.03 seconds, beating Michael Johnsons' record of 43.18 seconds set during the 1999 World Championships in Athletics in Seville, Spain.
Split into simpler sentences: In the 2016 Olympic Games in the men's 400m he won the gold medal with a World Record time of 43.03 seconds, bettering the former record from Michael Johnson (43.18). Johnson's record had been standing since the 1999 World Championships in Athletics in Seville, Spain.