I’m not sure what would count as “understanding” God from your point of view. I don’t think that it would be possible for us to completely understand God as He is infinite, though we may have a finite understanding of God that can always grow. However I think that omniscience is still intelligible. Lonergan’s proof is a logical proof that attempts to show this.
I’m paraphrasing and cutting out a lot of the supporting argumentation but it basically involves noticing that every object contains intelligibility which can be liberated from the object by an intelligent observer via an act of understanding. Every object that we know of cannot be solely explained in terms of the intelligibility contained therein (for instance a tree cannot be solely understood in terms of the data of the tree without recourse to understanding cells, photosynthesis, chemicals, atoms, etc.) If an object cannot answer all questions about itself, then its existence is contingent upon other objects who can answer those questions (i.e. the tree’s existence is conditioned by cells, chemicals, etc.). It’s intelligibility is said to be restricted. At the highest level is unrestricted intelligibility which leaves no question unanswered about itself, because if it did then you would have a higher level of being, leading to an infinite regress.
He then goes on to show that this unrestricted intelligibility is also a perfect act of understanding that understands itself. This is because the unrestricted intelligibility is not tied down in an object like the information in a tree. Since it has unconditioned existence it is an act of understanding of itself.