Complex sentence: Basly entered mining as a "galibot" (minor-young person) at the age of twelve, and later became the secretary of the Trade Union of the minors of Anzin when it was created in 1882, and its president in 1891.
Split into simpler sentences: Basly entered mining as a "galibot" (minor) at the age of twelve. After the creation of the Trade Union of the minors of Anzin in 1882, Basly became its secretary, and subsequently its president in 1891.