The Trinity is real. In Genisis, God said "let US make man in our image"....; when Moses asked the burning bush who he should say sent him, the reply was "I AM"; and in the gospel of John, Jesus said "Before Abraham was, I AM". And also in John, Jesus says the Father will send the Helper, the Holy Spirit....; The Holy Spirit is mentioned many times.
So from the beginning of the Bible, we have a plurality in God. The Father, the Son, and the Holy Spirit. Jesus referred to the Father many times; when Jesus was baptized, a voice from heaven said 'this is my son" and the Holy Spirit descended like a dove.
For ne argument about Jesus not being God because He died, wrong! Jesus the man suffered and died but the God part did not die; that Part was set aside so that He could suffer the punishment for our sins and take on the full wrath of God so that we could be spared.
Believe what is written in the Bible. Be saved. Or turn your back and suffer.