Can you give an example of how you implemented the Content Structure, Document Type, File Structure and Template structure?

Have you checked the documentation? https://docs.umbraco.com/umbraco-cms/tutorials/multisite-setup

Yes, I checked, but when creating the site, what kind of folder structure should I set up under Views and Partials, including property naming, plus what should the folder structure under Document Type be like?

That's totally up to you, it's difficult to help since everybody has a different opinion on that.

You could try checking out Umbraco Starter Kits which will have a Content structure already setup for you as well as the CSS, Views and Partials. A certain starter kit might give you the inspiration for how you want to structure your CMS. I personally like Clean by Paul Seal. https://marketplace.umbraco.com/category/themes-&-starter-kits