I'm trusting Cofty that you are aware that the trinity doctrine doesn't teach that the Father and the Son are the same person? And you are familiar with gobbledygook terms like modalism and Sabellianism?
And that your assumption that explaining the nature of God should be simple and couldn't be a mystery is contradictory in itself? Attempting to grasp fully the nature of an eternal being that by definition cannot fully be grasped by a finite mind is going to be challenging and to a degree conceptual.
Hope there weren't too many big words there for you.
Will have to reply later as I am at work.