Welcome, Dindin, and best wishes to your kitties! You are on the right track.

We humans are not allowed to really understand how and why cats become friends. But giving them time usually helps. In my house, I had an adult cat that really did not like a new kitten, and never did become friendly with it. But eventually tolerance reigned, and each ignored the other.

As others have said, watch for real fights, but noise and showing off is part of the process. I don't think it even helps much to interfere - but it can get you scratched up.

Good luck, and tell us more of your fur family when you get a chance.