Yea I'm deep into Hussein Al Rubaye 's "The Complete Android Kotlin Developer Course" and I'd give it an 85-90% rating. I'm learning more from him than anyone else but there are two problems. First is that he shows you how to use things like an inflater in the context of the app you're building, but you never really understand why it works or how to create your own in a different situation. Second, he teaches a number of very bad habits for Kotlin that Hadi Hariri warns about. Mainly, he's using !! instead of safe calls all over the place to get around null warnings, which is a null pointer exception waiting to happen.