So God is not understandable because he says he is LOL 
Humans had to work out what God is. Start from anywhere and you pretty quickly come to the conclusion that you can't know everything. God, to be God, has to be bigger. As humans we are only able to think of God in human terms. God is bigger than that of course, so we think we can give him some of our attributes that we could see fitting with a divine nature.
God can't lie. It isn't in our logical construct of him. & we can know for sure that our logical construct of 'God' is perfect. If it isn't, we need to improve it.

Humans had to work out what God is. Start from anywhere and you pretty quickly come to the conclusion that you can't know everything. God, to be God, has to be bigger. As humans we are only able to think of God in human terms. God is bigger than that of course, so we think we can give him some of our attributes that we could see fitting with a divine nature.
God can't lie. It isn't in our logical construct of him. & we can know for sure that our logical construct of 'God' is perfect. If it isn't, we need to improve it.