Studying abroad in Copenhagen and worried I won't be prepared before I get there

Making this post in case anyone who's done this before sees it and can reassure me a little or tell me what I need to do.

im studying in the social sciences at the university of copenhagen, just as a fee paying guest student, I'm from the US and it seems like a lot of the systems are different. When registering for classes, I used mobility online, picked four classes, submitted them, but now there is no sign that I did that anywhere? Like it doesn't even have a pending thing, and I'm scared I did something wrong. Should I be able to see those? Pretty sure I also have to confirm them in another portal, there's no way to find that... I'm sure its fine I just have this vision of me getting there and not being in any classes and not knowing what to do and freaking out.

the other thing, I'm planning on doing all my visa stuff when I get there, just printing out all the right documents, and going into the office one of my first days to get it. Pretty sure thats fine but want to check.

And now that I'm on a roll here, what about a phone number? can I keep using my usual number if Im on an international plan through my service provider?

Any reassurance would be nice! I leave in like 3 weeks, and am starting to freak out. So excited, but am not the type of person who is good at staying on top of things.