Complex sentence: At the 2010 World Cup in Germany, he set a personal best of 598; but not long after that, set a new personal best when he shot 599 at the 2010 World Cup in France.
Split into simpler sentences: At the 2010 World Cup in Germany, he set a personal best of 598. Not long after that, he set a new personal best when he shot 599 at the 2010 World Cup in France.