How did Christopher Columbus gain experience as a sailor and navigator?

Christopher Columbus gained his experience as a seaman and navigator primarily through his work in the Portuguese merchant marine. His maritime career included several significant voyages and roles:1

• Early Voyages: In 1477, he sailed to Iceland and [Ireland] with the merchant marine.1
• Commercial Experience: By 1478, he was working as an agent for the Genoese firm of Centurioni, which involved buying sugar in Madeira.1
• African Expeditions: Between 1482 and 1485, he traded along the Guinea and Gold coasts of West Africa. During these trips, he visited the Portuguese fortress of São Jorge da Mina, where he gained essential knowledge of Portuguese navigation techniques and Atlantic wind systems.1
• Chart Making: Based in Lisbon with his brother Bartholomew, he also worked as a chart maker, which contributed to his navigational expertise.1

While he was largely self-taught, this practical experience at sea, combined with his study of various geographical and cosmological texts, prepared him for his later voyages.21