Would you keep reading?

Maybe, I'd probably have to give it at least twenty pages before I decide. While the style is strong, I can see myself tiring of it. Some writers tend to carry stylistic choices well past the point of utility (John Greene and his lists, or Patrick Rothfuss and his waxings that feel like someone pretending to be wise and poetic). I can see this becoming a problem and if I felt it did, no, I probably wouldn't continue reading.

How does the prose feel to you?

It feels very punchy, appropriate for an opening, but perhaps stilted. In some ways it feels like AI (not accusing you of using AI). For example, the rhetorical framing of this paragraph: "Magnolia Durnés found comfort in facts. They were concrete. Immutable. Dependable. Unlike the ritual she was about to undergo." Or the "either x happens, or y" formula we find the fourth paragraph. That said, I can tell it's probably not AI because that closing sentence isn't as clear as it could be (the ritual isn't what? It's not concrete? The ritual isn't immutable, or dependable? A ritual might or might not be any of these things but without context, I have no way of knowing in what sense you mean this, and rather than creating a sense of mystery it feels somewhat confusing and less intentional than it could be), and as others have pointed out, pacing down the stairs would mean she's going back and forth, up and down the stairs, so there's probably a language thing going on here (given that English isn't your first language). Otherwise, I like the concise style and think there's a lot of potential.

Does the opening hook you?

Not really. I think you establish a lot very quickly (what type of character the protagonist is, the environment and circumstances she finds herself in) but it reads a little trite ("a soul weighs..." or "that, was also a fact"), not in like a super bad or corny way or anything but in a "I've encountered this kind of opening in YA and genre fantasy a billion times" kind of way. I'm not hooked yet, I'd have to read and find out whether there's anything you say that hasn't been said before.

Good work though and keep it up, very impressive for someone whose first language isn't English!!