I suggest you go through this hands-on tutorial before moving on to the Advanced one. Here, we will build up on the concepts of the Basic Tutorial while covering this one will help you a lot in the advanced one.
So, what's the end goal here?
It's quite simple (but not easy)... we will take an existing spaghetti code (from a YouTuber) and refactor it into a clean, modern, powerful and more secure application using composer packages. We won't use any framework, but rely on composer packages to get the job done.
WORK IN PROGRESS.