Complex sentence: Now around thirty years old, Amerigo used this interlude to deepen his studies of mathematics, cosmography and geography, and he is believed (albeit without much evidence) to have had a few meetings with the Florentine polymath Toscanelli before the latter's death in 1482.
Split into simpler sentences: Now around thirty years old, Amerigo used this interlude to deepen his studies of mathematics, cosmography and geography. Although concerete evidence is lacking, it is generally believed Amerigo had a few meetings with the Florentine cosmographer Toscanelli before the latter's death in 1482.