It is good for us not to know everything. It keeps us humble. God is bigger than us. There will always be mysteries and things we are not sure of.
You can know true things about something and yet not know everything about it. I know a fair bit about gardening, for example. I love seeing things grow. I have been enjoying picking mangoes and figs from my garden lately, and I have a fair idea how to grow most vegetables. I know the basics about gardening and soil and watering and fertiliser. But there is a lot I don’t know as well. I often come across some kind of insect that I don’t recognise. I have had plants die for not much reason. I have had to look for advice from garden centres or the internet when I get stuck on some problem.
Likewise, we can know true things about God without knowing all there is to know about God. The disciples in Matthew 14 are a great example of this. After seeing Jesus walk on water and then calm a storm, they fell down and worshipped him. They called him the Son of God. After such a long time, they had understood something important. Their master was God; for you only worship God. They had got it.
Yet they didn’t understand all that much if you think about it. In the following passages, we see them misunderstand that Jesus needed to suffer. They were concerned that the Pharisees were offended by Jesus. They made foolish suggestions at the transfiguration. In so many ways, the disciples didn’t know very much. What they did know was correct but not exhaustive.