Complex sentence: He became famous at age 19 as the singer, guitarist and songwriter of the popular Danish band Dizzy Mizz Lizzy, but when the band broke up in 1998, he has built up a very successful solo career.
Split into simpler sentences: He became famous at age 19 as the singer, guitarist and songwriter of the popular Danish band Dizzy Mizz Lizzy. Since the band's break-up in 1998, he launched a very successful solo career.