Not sure what you are saying here? Europeans brought written language, math, science, agriculture, and engineering to African nations (exceptions are some of the Arabic ones in North Africa—but these are not negroes). Have you seen any of the cities in Africa. They were not designed, engineered, and constructed by African ingenuity. So, to say there were no successes is ludicrous.
Not sure what you are saying here?
Then let me say it slower for you:
"Once - the - Europeans (read: White people) - left - their - colonies - in - Africa - , they - all - devolved - into - basket - cases.
The - native - Africans - could - not - maintain - the - schools, - roads, - hospitals, - or - the - general - economies...".
Is that better?