[Beginner] I created a static page that looks decent full screen but gets butchered the smaller the window gets. Any tips or recommendations on where I can learn proper scaling and display from?

I'm very aware that this is all the issue with my code. I'm very new to HTML and I've been learning things from YouTube and while the implementation has been decent, I clearly need to learn to scale my elements better. Or anything else that can help me keep my website presentable on different screen sizes. Sorry if that's a dumb question. Any help is appreciated!