I'd always go with Big Nerd Ranch books regarding Obj-C. The language didn't have any large changes lately, so dated is no problem. As soon as you know the basics, Swift is easily translatable to Obj-C (or the other way round).
Here is one Big Nerd Ranch book, but maybe there is a more current:
https://www.amazon.com/Objective-C-Programming-Ranch-Guide-Guides/dp/032194206X
I used this book when i started learning objective c:
https://www.amazon.com/Objective-C-Programming-Ranch-Guide-Guides/dp/032194206X/ref=dp_ob_title_bk
>!Also available as pdf for free if you search hard enough... !<
I really liked it and learnt a lot. I read their book on iOS programming after that one (latest edition uses swift, earlier editions uses obj-c).
You can try "Objective-C: The Big Nerd Ranch Guide" for a basic primer on both C and Obj-C if you're not familiar with topics like pointers and/or have minimal programming experience overall - it's really an intro book. It also has a bit of info on most of the basic Foundation Framework classes like NSString, NSArray, various collection classes, and some info on memory mgt. It's obviously a bit outdated so the projects and XCode examples probably don't work, but it's a good intro.
Ray Wenderlich has an Obj-C Style Guide that could be useful and has some links to documentation.
Main reference would probably be Apple's "Programming With Objective-C." and the "iOS Programming Guide", which still has a dropdown for switching between Obj-C and Swift.
You are not alone. I tried to learn programming three times before I succeeded on the fourth try. It is really just a matter of finding the explanation that works for you. You haven't found that yet.
Here's what worked for me: I read Aaron Hillegass' Big Nerd Ranch book on Objective-C. The way he explained things just made sense (to me). It's here: http://www.amazon.com/Objective-C-Programming-Ranch-Edition-Guides/dp/032194206X/
(There is a Swift book coming out next month if you'd rather wait for that, can't speak to the quality yet but here's the link: http://www.amazon.com/Swift-Programming-Ranch-Guide-Guides/dp/0134398017/)
After finally learning, I made a course for people who had struggled like me, focused on explaining concepts in real-world language. If you PM me I'll send you a free coupon code and a link to a Code Concepts cheat sheet that hopefully will help.
Best wishes -- don't give up unless you actually hate coding. If you think you might love it if you could only grasp it, keep trying! The wall you hit does not mean you're stupid; most people hit that wall and have to get past it. It's just that almost no one warns you about it in advance, so it can feel like you're the only person not getting it.
If you're just starting, I'd suggest Big Nerd Ranch's Objective-C Programming. http://www.amazon.com/gp/product/032194206X?ie=UTF8&at=&force-full-site=1&ref_=aw_bottom_links
A couple of questions:
If you have a PC, you can only develop for Android. If you have a Mac, you can developer for iOS or Android.
I highly recommend a book over a website. They are much more comprehensive and go into greater detail.
Mac/iOS uses Objective-C. http://www.amazon.com/Objective-C-Programming-Ranch-Guide-Guides/dp/032194206X/ref=sr_1_1?ie=UTF8&qid=1419300572&sr=8-1&keywords=big+nerd+ranch+objective+c
Android
Big Nerd Ranch books are awesome.