Ruby's behaviour is weird if you're used to many other OO languages, but it shares that weirdness with other languages influenced by Smalltalk, such as the Magik languages used in the Smallworld GIS.
Both ideas of what private means make sense, but I can certainly understand the confusion they cause if you expect one behaviour and discover your language does something different.
That's why I always approach new languages as a complete beginner. It's tempting to jump into the deep end thinking you know the basics, but in my experience it has a lot of pitfalls.
I like to find a book or "web book" with exercises such as http://JavaScript.info and just follow it. Read it and do all the exercises. It takes some time and some times it feels a bit like the exercises are too easy, but often times I find that they are deceivingly complex precisely because I'm misunderstanding something. It's like a win/win, either I do the exercise in a few minutes because it really was easy, or I learn something.
I enjoy entering zen mode and just banging out a ton of exercises. I see a lot of people consuming video tutorials/courses without exercises and I think they're doing themselves a disservice. They get to chill and just watch a video and feel like they're learning but most of the time they really arent. I see people waste hours and hours watching courses or transcribing code from tutorials and the moment they try to do anything on their own they realize they have absolutely no idea what they're doing. It's just a huge waste of time.
People are different and stuff but I don't really buy the whole "people learn differently" thing. Everyone learns best by doing, and the structured "read about a topic, then test your knowledge by completing tailored exercises for that topic" approach allows you to have a linear and thorough path from zero to fairly advanced. I've tried books without exercises and I hated them.
I'm not opposed to looking up videos on specific topics you struggle with, but I think videos are best used as a supplement rather than a primary form of education.
Both ideas of what private means make sense, but I can certainly understand the confusion they cause if you expect one behaviour and discover your language does something different.