If you don't know anything about coding, start with the basics. I suggest learning C first and then when you have basic knowledge on how variable types work (int,double,float,void and etc...) And conditional statements (if,else,while and loops), start going deeper into the core and learn everything about Object-oriented programming (OOP)
I posted a topic on a book that I read, it has great reviews and it can also be used as a reference while coding. Book : https://iosgods.com/topic/43879-learn-objective-c-for-beginners-make-iosmac-applications/#entry1412956