Where to go next
An empty folder is now a site with a homepage, a page, a post and two languages, which is deliberately thin. Every part of it has a guide that goes further on the topic.
Next steps
The assets pipeline. You wired a stylesheet in about five lines. The assets pipeline guide covers what happens either side of that: PostCSS on the way in, esbuild for scripts, and the inline filters for critical-path CSS.
The head. You dropped <baseline-head> into a layout and got a full <head> back. The head and noindex guide covers what lands in it, and how to keep a page out of search results when you want to.
The sitemap. It appeared without being asked for, which is the point. Sitemaps and drafts covers keeping pages out of it, and writing drafts that stay in dev.
Deploying it. The build you ran claimed an origin you passed on the command line. Making that true in production is deployment checks, and if the site lives under a subpath rather than at the root, deploying under a subpath is the one to read first.
More languages. You wired two. The multilang module reference has the full activation rules and helpers, and filters covers the translation-aware ones. Localising nav labels and other UI strings is translating UI strings.
One thing worth knowing
If you find yourself writing permalink and layout into every page's front matter, the rules you set up in the directory data files have stopped doing their job, and content organisation is where to look.
From here the guides can be read in any order. Each one assumes the site you just built.