Complex sentence: It is estimated, Gorontalo has been around since approximately 400 years ago or around the 1500s in the 16th century.Previously Gorontalo City became one of the centers of Islamic religion in Eastern Indonesia, in addition to Ternate (now part of North Maluku Province).
Split into simpler sentences: It is estimated, Gorontalo has been formed since approximately 400 years ago or around the 1500s in the 16th century. Gorontalo city at that time became one of the centers of Islamic religion in Eastern Indonesia, in addition to Ternate (now part of North Maluku Province).