Complex sentence: The Oba of Bini then sent a trade expedition by sea which declined to engage the people and returned to what is now called Benin City where he reported to the Oba of Bini that they were attacked.
Split into simpler sentences: The Oba of Bini then sent a trade expedition by sea. He declined to engage them further and returned to what is now called Benin City where he reported to the Oba of Bini that they were attacked.