Jesus prayed to God “not my will, but yours, be done” because Jesus and God have separate wills (Luke 22:42; John 5:30). They would have one will if Jesus and the Father are the same “one God.” Trinitarian doctrine claims that Luke is referring to the human will of Jesus, and not his divine will, but that is problematic because the Bible never says anything like that or even hints that Jesus had two wills in conflict with each other inside him allowing one to be human and the other to be divine.
The Bible says Jesus is an “heir” of God (Hebrew 1:2), and a “joint-heir” with us (Romans 8:17). But if Christ is a co-eternal “Person” in the “Godhead” then he cannot be an heir “of God” because being God would put him into a position to be a full owner of everything and that would mean there would be nothing he could “inherit” which is why Jesus cannot be God and an heir of God at the same time. The Bible says that Jesus Christ is the “image of God” Colossians 1:15; 2 Corinthians 4:4). If Christ is the image of God, then he cannot be God because a person cannot be himself and an image of himself at the same time. Jesus can be called the “image” of God because he always did the will of God, and because he was the image of God is why he could say you had seen the Father if you had seen him.
Ephesians 4:4-6 says there is one God and one Lord and one spirit. This verse teaches exactly what the Jews expected based on the Old Testament and what Jesus, Peter, Paul, and others taught: that there was one God, one Lord, and one spirit of God. 1 Corinthians 8:6 says “for us there is one God, the Father… and one Lord, Jesus Christ.” This simple and straightforward language elucidates that the Father is God and the Son is “Lord” making a clear differentiation between the two.