Don't understand the Trinity doctrine

Question

Tried to understand the doctrine deeply and in a broader way than it is taught in school, or presented in Wikipedia.

And no one can explain it to me in a simple way for my mind to accept it, How it can be that:

x = G 
y = G
z = G 
BUT! 
x != y != z != x

And even in this site the authors of the site have written without no doubt:

The most difficult thing about the Trinity Doctrine is that there is no way to adequately explain it. The Trinity is a concept that is impossible for any human being to fully understand, let alone explain

In the end the authors just throw at me their problems:

This is a difficult concept to grasp. But let's put a God-sized doctrine into perspective -- God is beyond our comprehension.

Logically, something does not work out for me, The Almighty will not allow us to believe that there is a triangle with four sides, or that he will create a square whose diameter is equal to its side. Of course it "is a difficult concept to grasp", because maybe they have disrupted the intent of Christ, who can tell me that Christ accept Tertullian:

new theological concepts and advanced the development of early Church doctrine.

I'm desperate to understand the truth, and to settle this problem.