Searching for sourcess on African subjects in databases can be complex, because there are a number of levels at which you can search. You can search at the:
If you search at the continental level, the sources you find will have a tendency to talk about Africa at the that level, giving broad coverage of topics, but will not necessarily deal with the subjects in specific parts of the continent, in specific countries, or amongst specific people groups.
So you will probably need to search at the lower, more-specific levels as well. Here are examples of some possible searches:
East Africa AND economics
Nigeria AND government
Yoruba AND sex roles