Complex sentence: His personal best in the 400 metres hurdles is 49.19 seconds set in Tampere in 2013, the smae year that he won a silver medal in the 400m hurdles at the European U23 Championships and was a semifinalist at the World Championships.
Split into simpler sentences: His personal best in the 400 metres hurdles is 49.19 seconds set in Tampere in 2013. He won a silver medal in the 400m hurdles at the 2013 European U23 Championships and was a semifinalist at that years World Championships.