Complex sentence: Oceania was explored by Europeans from the 16th century onwards, the Spanish, with Ferdinand Magellan in the expedition achieved the circumnavigation of the world for the first time, discovered the Marianas and other islands of Oceania.
Split into simpler sentences: Oceania was explored by Europeans from the 16th century onwards. The Ferdinand Magellan expedition achieved the first circumnavigation of the world and discovered the Marianas and other islands of Oceania.