Difficult to pin down specific sites aimed at accepting Africans. Its probably best not to approach it that way as writing jobs tend to go to the writers whom demonstrate a firm grasp on the use of the english language - which you seem to have.
I recommend you take a look at my hub as i update the hub each month with sites aimed at finding you writing jobs. These lists have kept me in a job for 2 years.
I am preparing a hub aimed at review sites and 'extra money' sites though these tend to be very low paid options and you are better off pursuing proper roles. The exception here is if you are trying to market a niche web site and just want traffic - again a whole new ball game.
If its a writing job you need, check my list.