Whether you are completely new to building, or coming in from an alternate design ecosystem such as Architecture or Traditional Art, this category is the one that lets you in to what Mona requires to make the best spaces that run smoothly on desired devices.
A lot of these elements fall under the category of 'Game Development'. Unity is a Game Engine after all. There are tons of resources out there to learn the applications you choose to make your assets. That said, many of the elements are covered in more detail on the sidebar on the left under the Create your Space, Improve your Space, and Optimise your Space categories.
You can always find more resources on Youtube to help you. There are a lot of builder recommended tutorials on the Tutorialspage as well.
Of course, you can always jump into the Discord and ask for help there! There are always people helping each other create the best worlds they can.