Complex sentence: Gus G. was recommended to them by David T. Chastain and played all guitars on the three first albums, but left in 2005 in order to spend more time on his own band Firewind.
Split into simpler sentences: Gus G. was recommended to them by David T. Chastain. He played all guitars on the three first albums, but left in 2005 to spend more time on his other band Firewind.