From the mid 15th to the 16th century men were very interested in finding new routes to get better trades and new lands
Henry the navigator who was the prince of Portugal at the time went to north Africa out of curiosity and in hopes to attack the Arab power and also looking for profitable trade.
and when they arrived to North Africa they tried to divert the Guinea trade of gold and ivory from north Africa to Portugal
In 1445 a Portuguese navigator named Dinis Dias reached the nile river
And in 1455 and 1456 Alvise Ca' da Mosto had traveled to the Capa Verde Islands
Diogo Cão, who was Henry the navigators captain had discovered the congo river. They had also made good trade with the riverine people.