If you know the English alphabets and the grammar, and have a decent vocabulary (know the meanings of generally used words), you have the ability to read any book written in the language and to communicate your thoughts in that language. 

If you understand Newton's laws of motion, you can make predictions on speed and location of moving objects in the world to a large extent. 

As we progress through school, we learn the basics and build on them over the years. The fundamentals of arithmetic that we learn in class five help us later on in high school to solve equations in Physics and Chemistry. The curriculum in schools and universities are designed to teach the fundamentals and to build towards increasing levels of abstraction from the deepest of fundamentals. 

We go through a similar learning curve from basics to more complex topics in every aspect of our lives, and we continue to do it all through our lives. 

If you're finding something to be hard to understand, it's because you're lacking a pre-requisite. You're lacking some of the fundamentals needed to understand what you're trying to.

Go back to the fundamentals and derive your way up. 

The ability to do this in a variety of fields is one of the most valuable skills.