Complex sentence: It completely replaced "Banan" within a few years, and Landskrona BoIS became in the same year one of the twelve clubs that participated in the first Allsvenskan, the finest assembly within Swedish football.
Split into simpler sentences: It completely replaced "Banan" within a few years. And Landskrona BoIS became in the same year one of the twelve clubs that participated in the very first Allsvenskan, the finest assembly within Swedish football.