Complex sentence: He began his career in Denmark and in July 2004 had a trial with English side Norwich City, before signing with Ajax in the Chelsea in July 2006, before his career ended in 2008 when he retired from football, because of injuries.
Split into simpler sentences: He began his career in Denmark and in July 2004 had a trial with English side Norwich City, before signing with Ajax in the Netherlands. He signed for Chelsea in July 2006, before his career ended in 2008 when he retired from football, because of injuries.