How did trade affect west African societies

Do you mean slave trade? Well ... The slave trade had many effects on Africa. Most of them were, of course, negative, although we can argue that the slave trade was positive for some African states at least in the short term. One negative about the slave trade was that it tended to increase the amount of war that occurred in West Africa. The reason for this is that European (and American) slave traders did not simply go out into the African countryside and kidnap their own slaves.