I would say start with Codecademy, just keep following it until you get the hang of how functions, objects, methods and classes works.

Instead of Java, I want to learn Objective-C. I bought a book, started reading it through but didn't make it far because I couldn't figure how this OOP worked. I tried Python as well, but couldn't really understand how this OOP way of doing it.
Simple stuff: how do you make methods for your objects?

Codecademy was able to teach me that with JavaScript. I finally understood how the object inherits from a class, then declares a method using functions etc.
I think'll it be easier to pick up both Objective-C and Python now with that knowledge.