My friend and my cousin ask me that I question and I couldn't tell them.

What language can you understand but can't speak? What is your mother tongue?

Creole amd my mother and father are haitian. Mostly all of my family are haitian.

It takes different skills to speak something, but when some languages are similar we often can understand them ( or at least part of them,) this is a normal thing to happen.

I can understand some German, but can only tell you the window is open to speak it.