I've heard that matter makes space curve, what does that mean?
Matter itself does not make space curve. When matter becomes dense enough its gravitational field increases, it is the gravitational field that curves space. Everything curves space and time from the smallest grain of sand, you and I, to the biggest sun in the universe. The thing about it is that on a scale the size of a human there is not any real measurable effect on space curving.
I think this question is better for seriousadvice.com! oh an I think it means that matter, having gravity holds space in "shape" so that speed remains teh same? but dont listen to me im in 9th grade.
Matter can make space curve if it is dense enough, that is the gravitational pull or electromagnetic pull can bend both space, light and the theory is time.
No, it is the effect of gravity thay make space curve.