Thomas Aquinas and infinity.?

because you need a First Cause- what Aristotle calls the primum movens the immutable principle that makes the world turn round. nothing could exist without a First Cause. That is, God. If that is obvious, it's very hard to prove that this First Principle is the God of Christians, a personal God. and that is the fundamental problem: what does Aquinas prove finally? Only the necessity of a first cause. And yes, it is necessary for all things to have a cause as long as they exist. If the First Cause will need another cause etc., this would mean that Being is founded on Nothing so everything is nothing.