I would suggest mastering vanilla HTML+CSS before moving onto frameworks. It'll be much easier to understand once you know the basics.
WebDev
Community for all things Web Development related.
I would read up on flexbox and grid, here are some games to practice:
http://www.flexboxdefense.com/
https://flexboxfroggy.com/
https://cssgridgarden.com/
You can do everything on your own, check out keyframes and transform. Play around with it!
https://animista.net/play
The website uses VH instead of SVH for vertical positioning. That’s interesting.
In terms of how to learn web development, it’s a long winding complicated process. I’d suggest to learn HTML, CSS and vanilla JS, then going with React and TS. Once you go through basic courses / documentation on those, you can try making some proper full fledged websites.
The x.ai website looks very simple and can be recreated (in terms of visuals) with only HTML and CSS.
The way to learn if you have no idea where to start is to start learning, get a bunch of courses on Udemy, or just watch YouTube, or maybe there are some courses on Coursera.
Until you at least have a solid grasp of what is a website and what are the basics of creating them, I’d strongly advise not to bother with trying to recreate anything.
Just dive in, try! It's like one page or two right? If you don't have the technical skills yet you can go with the fundamentals and just use vanilla js, CSS and HTML. But if you go with a framework shouldn't be too bad either. They make a lot of aspects of the development easier but I do believe that you need to have a proper grasp of the fundamentals