Complex sentence: Frédéric Chopin's Piano Concerto No.2 in F minor, Op.21, was composed in 1830, before he had finished his formal education, and very shortly before his Piano Concerto No.1.
Split into simpler sentences: Frédéric Chopin's Piano Concerto No.2 in F minor, Op.21, was composed in 1830, before he had finished his formal education. Although it is numbered second, it was composed very shortly before his Piano Concerto No.1.