I think that Jesus is a prophet that was sent to spread the message of God just like the many prophets that came but because the holy books continued to be altered and people came back towards corruption, more holy books were written and more prophets were sent until one holy book wasn’t altered
To be honest, it doesn’t make sense to me to think of God as three parts but rather one God so I get your confusion
You’ll just have to do some research and perhaps read in to other religions to because a lot of them have similar beliefs to an extent.