In Evangelii Gaudium, Pope Francis describes a human reality: it is unlikely and unrealistic to expect the entirety of Church teaching to be comprehensible to all. Jesus had his partial success stories too. Peter didn’t turn out so bad.
The priority is the assent of the heart (not the mind) as revealed in the life witness of the disciple:
42. All of this has great relevance for the preaching of the Gospel, if we are really concerned to make its beauty more clearly recognized and accepted by all. Of course, we will never be able to make the Church’s teachings easily understood or readily appreciated by everyone. Faith always remains something of a cross; it retains a certain obscurity which does not detract from the firmness of its assent. Some things are understood and appreciated only from the standpoint of this assent, which is a sister to love, beyond the level of clear reasons and arguments. We need to remember that all religious teaching ultimately has to be reflected in the teacher’s way of life, which awakens the assent of the heart by its nearness, love and witness.
That seems difficult, but rather clear to me. Faith in Christ can be understood on a level beyond reason, argument, and even apologetics. It would be impossible to understand everything–as mortal human beings, this much should be clear. It is at that point the heart must take over.