You will catch up on both. You just need to listen to people a lot and participate in their conversations! They speak french in big businesses (considered as a courtesy language) and Creole.
Note that Mauritian Creole, also called Morisyen, is a creole language or dialect from Mauritius. Almost all of its vocabulary stems from French, with smaller numbers of words from diverse sources such as English and Portuguese.
Even when being a Mauritian, and having studied both of the languages up to now, I must admit that my French is not perfect. Some words in Creole just pop out from my mouth now and then after speaking in French after 15 mins or so on a slip of the tongue. That's inevitable as both languages have so many words in common that your brain sometimes tries to roll back on your mother tongue.
Well the thing is that my friends and I really enjoy playing pranks or annoying the bloke among us who has just mispronounced a word....although I dunno why we do that! But it's really bad manners to laugh at someone who has done a mistake in pronounciation!