Can't understand CI4 services and factories! Lack of OOP knowledge ?

Hello guys.
I have been following CI for many years. In fact since v2. I built a dynamic league site using v3 mainly based on procedural programming. But for many reason I have decided to create a new one entirely on v4 because it supports latest php updates and new way of routing and classes. 
But when I want to learn routings, services and factories it's like I have to remember and copy paste the code inside the file. Is it because I should learn OOP programming first?
I appreciate if you guys can guide me through. How can I improve my skills and resolve this so I can move forward and get along with the new stuff.
Thanks.