English is difficult

Recently, my friend told me that she should use more 'difficult' English.
Since then, I've been thinking what is 'difficult' on using the language.

I think three kinds of difficulty.

First, I regard this word  is difficult when I cannot understand the meaning of the word.
For example, there is a sentence that

'John is like Picasso.'

If I've never seen the word Picasso, I 'll get confuse.
I'll look up Picasso in dictionary, and find out that is artist's name.
It will easy to overcome. I need only dictionary.

Nest, I feel this word is difficult when I cannot understand the concept of the word.
For example,

'John can use the theory of relativity.'

Theory of relativity? I cannot understand whole concept of this word if I look up 'theory of relativity' in google. I'm not good ant mathematics.
It is difficult to overcome because I need to spend a lot of time to study the concept of the word.

Third, I feel this word is difficult when I cannot understand why this word is used in the sentence.
For example,

'John can use the theory of relativity, so he is like Picasso.'

I cannot understand what mean theory of relativity and Picasso in this sentence only using dictionary.
There is no explanation what connection between theory of relativity and Picasso.
However, this problem can overcome if writer add more explanation, like

'John is only eleven years old. However, he can use the theory of relativity, so he is like Picasso.'

Then, if I know Picasso's history well, I can understand that writer mention Picasso to compare with John's and Picasso's talent in young age.
If I don't know Picasso, writer should add like

'John is only eleven years old. However, he can use the theory of relativity. Picasso was a genius in drawing at young age, so John is like Picasso.'


These examples are not good.
Maybe writer should write only 'John is genius.'