There are two types of theology. Cataphatic and Apophatic.
Cataphatic theology uses positive statements to talk about what God is, like "God is Love". These statements are true and they tell us truths about God. However, we must always also be aware that they are limited by analogy. In other words, we are talking about God using our own finite minds and finite experiences. This means that what we say, and the understanding that we derive from it will always be limited.
God is infinite, and as such, it is impossible for us to comprehend him or his nature.
We can depend upon statements like God is Love, God is good, God is eternal. But those things are really very limited and they don't come close to allowing us to comprehend God or his nature.
Apophatic theology relies on talking about what God is not. Here we make distinctions between God and our experiences etc. So we can say that God is love, but he is not love in the sense that humans experience love with need, because God has no need. He is not love in the sense of passion, where we are driven by love and it makes us suffer, because God does not suffer passions.
This is why Christianity necessarily involves a mystical element. We can know God by direct relationship, but we cannot know God by intellectual comprehension.
Think about it like this.
An infant who cannot speak or comprehend speak, with extremely limited mental development, cannot know their parents. In a certain sense their parents are an absolute unknowable mystery to them, completely beyond their comprehension. They also know almost nothing ABOUT their parents.
Yet they are capable of having an intimate relationship with their parents because love transcends intellect and knowledge in that sense. They can have perfect trust in their parents. They can have communion with their parents. All transcending their capacity to know in the traditional sense.