French is merely an "official" language of the Democratic Republic of the Congo. That doesn't mean people speak it natively, or even speak it at all.
Same goes for Abidjan, located in Ivory Coast, where the vast majority of people speak native tribal languages, but where roughly 30% of people have learned French as a 2nd language, due to the fact that it is a designated "official" language of Ivory Coast.
Official language doesn't mean they speak it.
Fun fact, the United Kingdom doesn't even have an official language, yet 95% of people speak English natively.