The preferred audience helps you choose the preferred audience for this post. Choose the people you'd like to reach in the News Feed (this feature is available for Facebook only). 

Preferred audience allows you to schedule / publish content organically by selecting the audience you want by interests, age, location, and language. 

Using the preferred audience you can schedule content for the English audience only, and then create another post for the French audience.

Here's how you can do it. 

2. Then, click on it and select Audience restrictions > Languages

Then choose the language you want this post to focus on. 

Unfortunately, creating a multi-language like on Facebook is not available due to Facebook API limitations.