as for the use I do the french language, I would bart it for any other language. Nice language but quite irrelevant outside cuktural interest.

Maybe once Africa will start to become center of economy in the next 10/20 years at least, French could be useful to use in colonies.

But actually africans are learning chinese

so go for CHINESE, folowed by russian,spanish and arabic.

Then if you are looking for languages that shape the brain to be lernt at small age. Indi or Italian

Indi for mathematic and computer/science and italian for problem solving and free thinking