Complex sentence: Mário de Castro (30 June 1905 in Formiga--29 April 1998 in Formiga), was a football striker from Brazil, who played his entire career at Atlético Mineiro, with whom he won 3 Campeonato Mineiro titles, of which he was top scorer twice.
Split into simpler sentences: Mário de Castro (30 June 1905--29 April 1998), was a Brazilian footballer who played as forward. He spent his entire career at Atlético Mineiro, with whom he won 3 Campeonato Mineiro titles, a competition of which he was top scorer twice.