"Are you from Kenya cause Kenya not" is just a play on words which is called a pun.

It's a humorous way to tell someone to stop doing something. Imagine someone picking their nose in front of you, and you want to tell them to stop (can you not [pick your nose]), but also look cool while doing it (in front of other friends). I think it's called a put-down.

Haha . let's hope someone let us know then

I don't understand it either.