How to learn structure of web application with python tornado

I can develop something like a blog service that works with a simple mysql with tornado. However, when I look at the web application code for tornado that other developers have posted on github, it does not have the same application structure as in the official documentation. https://www.tornadoweb.org/en/stable/guide/structure.html

What I want to build and may build in the future is a very general web application. I would like to know how to design around DB, what is considered a good configuration for a simple web application, clean architecture that is the talk of the town, etc., and how to separate the configuration? I would like to learn how to write a I would like to know what materials and sample code you would recommend. I am stumped as to where to start. If there is a community I can ask questions or study with, I'd like to know that too!