Why do Christians say they understand god's nature/trinity;& when contradictions come say that god's a MYSTERY?

I am a Christian who has asked this question millions of time because I don't believe in the trinity bullcrap that a lot of believers believe in. You are about to get some stupid answers and question about this question. This is something lazy people have been taught to believe instead of going back and rereading the lies that the preachers teaches them. Jesus also says that he doesn't know the final hour or day of the world ending but yet a lot of Christians believe that he does. Making Jesus a liar. But they won't call him that but will say that he does know but he doesn't know since he was in the human form. Yes the same human form that he has now. The only thing difference is that the human form he has is clean without all the flogging marks. But hey this is what happens when you put your trust in man instead of reading and allowing God to teach them.