Unity dude here, learned alone/self taught-

Being old enough to enjoy reading technical books/articles is a + and knowing the acronym RTFM

I learned about collection types other than array/list from reading this article by the creator of the game Project Zomboid- as he used Stacks for zombie behaviors https://ia600303.us.archive.org/18/items/pdfy-G4Wm9sq1LU298r...

Then I got this book which is a great overview of C# for use in Unity https://csharpplayersguide.com/

Remembering which ones are FIFO and LIFO helps you remember what is what for etc

But yeah- had to read an article and a book- I hated most of the Unity youtube tutorials- enough info/help to get you going but they leave you stranded in the woods without a path out because you were blinding following someone else when you walked in.

Better to read/learn and understand the small bits yourself slowly as they are the breadcrumbs that lead you out.