How to learn object oriented progarmming

I am studying at Faculty of Electrical Engineering and Computing, and I have a subject OOP (object oriented programming) in Java.

That is the only subject that i did not manage to pass continuously. We have presentations and lectures, but they are (in my opinion) not so good.

My question is: How did you learn object oriented programming, what book/online course/YouTube channel did you use to learn the paradigm?

Thank you!