Its a matter of practising,if you see guys who are really fluent like koffi,wazekwa,jossart,kibens and co its either guys who have studied in europe or guys who have carried a constant practice of that language
in some other african francophone countries there is also that "problem" of an extreme majority of time of using national languages(which is not a bad thing) at expense of french,so you find guys who have studied in french,got diplomas in french but still cant speak well to save their lives lol