Wait until you hear about relativity.

And also we don't know that C is the limit entirely, but it is so far. Also, we don't know if there are more dimensions in our reality or not because we cannot observe them. And no, I don't have much of a better answer.

Basically, we still know we don't know a lot, and we probably don't know a ton of what we don't know that we don't know. Also magic.