When the Americas was selling raw materials to Europe, it needed cheap manpower to gather it. So they opted for SLAVERY. Africa itself sold and traded it's people to make profits, this was all in efforts of MERCHANTILISM.
THE MIDDLE PASSAGE was one of the worst transportation means of all time. Slaves were stuffed in small compartments and overly crowded. They sat in their own filth, a lot died from disease or suicide.
Once they arrived at the COLONIES they were traded off to plantations or other places of work. Dehumanized and abused, the TRIANGULAR TRADE made it easy to gets slaves from place to place all over the Americas, England and Africa.
Due to forced labour, the ECONOMY progressing steadily. Slaves harvested sugar cane, cut wood, and in some places cocoa, as well as many other products.
Slaves were treated very poorly and didn't live for very long. The south part of the Americas had more slave trade since they were treated even worse, while the North tried to have slaves born to profit off it.
When slavery was eradicated, Africa could make no longer profit off the triangular trade and fell economically.