This is new with OneUI 7. If you swipe down from the left, it gets you notifications, swipe down from right gets you the quick settings. You can, as you already know, swipe left and right between these screens once they are pulled down. I haven't owned one in a while, but apparently this is more like how an iPhone works. You can change this back to the old style. Once you've swiped down and have the quick settings screen, tap the pencil in the upper right hand side of the screen. You'll see a tab in the upper left corner that says panel settings, tap that. Change from separate to together. That will get you back to the old style pull down.
Edit: And apparently it took me 10 minutes to write all of that. Lol!