Complex sentence: He would become the 14th navigator in western history, and the first Frenchman, to sail around the world, and the completion of his mission would bolster the prestige of France following its defeats during the Seven Years' War.
Split into simpler sentences: He would become the 14th navigator in western history, and the first Frenchman, to sail around the world. Completion of his mission bolstered the prestige of France following its defeats during the Seven Years' War.