Complex sentence: He transferred to Bayer Leverkusen in 2001, where he played until 2005 when his contract expired, he turned down an offer from English club Everton to join Celta de Vigo.
Split into simpler sentences: He transferred to Bayer Leverkusen in 2001, where he played until 2005 when his contract expired. Subsequently, he turned down an offer from English club Everton FC to join Celta de Vigo.