Dr. L. Russ Bush III teaches on the doctrine of the Trinity. Most explanations of the Trinity begin by stating how the Trinity is a mystery that we cannot explain or is beyond our understanding. However, Christianity is uniquely trinitarian, and to say that we do not understand the Trinity is to say that we do not understand Christianity.
How much of any topic do you need to fully comprehend before saying that you understand it? Do you need to be able to answer every question it is possible to ask about a topic, or is it possible to know all of the given facts and still say you understand? We don’t know everything about God, but we do know something about God, and we can know that those things are true.
We may not be able to answer every question anyone will ever ask, but we can know the facts presented in Scripture. The bible is a revelation of God, written with intent that we understand its content, not with the intent of confusing everyone.