Well, learning Java OOP from scratch is a great initiative towards learning Java Development. I am also a software developer, and in my opinion, if you want to learn Jave OOP, then I will recommend you learn from simple basics and then understand the concepts of basics and logic that will help you to build a strong foundation.
Here is the official website where you can learn java online https://www.learnjavaonline.org/ - here you can learn about basics and many more.
Secondly, I have seen this article where the author wrote about the concept of OOP, which will help you in learning.
Happy learning.
Thanks