Complex sentence: He trained as an actor at the Mozarteum in Salzburg (1955--1957) and was always profoundly interested in music: his lung condition, however, made a career as a singer impossible.
Split into simpler sentences: He trained as an actor at the Mozarteum in Salzburg (1955--1957) and was always profoundly interested in music. His lung condition, however, made a career as a singer impossible.