Hi!

Dark matter is part of what is coined the Standard Model of cosmology. Therefore, it impacts the properties of the universe. But this is not the only unknown ingredient. There is also dark energy that is itself responsible for the expansion of the universe. And the two can be fully unrelated, or related (there are some constructions where they are). In short: we don't know (which is the reason why it is interesting)

I hope my answer clarified a bit. Otherwise, feel free to come back to me.

Cheers!