Complex sentence: He ran a personal best time of 44.94 seconds in reaching the semi-final in the individual 400 m event and as part of the Great Britain team, finished fourth in the final of the 4x400m relay-0.6 seconds away from a medal.
Split into simpler sentences: He ran a personal best time of 44.94 seconds in reaching the semi-final in the individual 400 m event. As part of the Great Britain team he finished fourth in the final of the 4x400m relay-0.6 seconds away from a medal.