Hi Noelle. "M'ap manje" does translate to "I am eating" (present). "Mwen pral manje" (or m' pral manje) is the equivalent of "I will eat". However, just like you might say "I am eating with some friends later" in English, some people also say "M'ap manje pita (later)" to indicate the future. But the correct and standard way to say it is "M'ap + verb" for I am + ing verb, and "Mwen pral + verb" for I will + verb.
Hope that helps. Let me know if you need more clarifications.