God is not 3 different people, Christ tells you in His own words, He and the Father are one.
God says in the Old Testament that He will stretch out His right hand, and that /HE/ will do valiantly. God refers to His right hand as a person, and that person is the Messiah.
If you want help understanding how Christ and God are one, imagine if I took my right arm, and sat it on the closest table to you. Id be here, in my chair writing to you. And Id also be there, in your living room, through my right arm
"His name will be called Emmanuel", that means "God, with us". "They will call Him wonderful, counselor, the Almighty God". The prophets of Israel understood what the Messiah will be, He would be God in the flesh, come to save man from their own evil doing.
Islam is /not/ of the God of Abraham, and it preaches an entirely different story. In fact, the whole reason we believe that Christ died on the cross, according to the tar-firs, is because allah made the man on the cross look like Christ. So the whole reason we believe in Christ, according to allah, is because allah deceived us into believing it was Christ. And allah calls it sinful for us to believe in Him. Does that really make any sense to you? I mean why would allah even do this to begin with? It served him no purpose, and apparently he is angry that we believe in Christ, even though its apparently his own doing. If Christ is coming not to save Israel, like He said he is, but to tell us He did not die for our sins, like allah says He is, then why did allah make this happen anyway? None of it would have had to have happened if it wasnt for allah doing this with no clear purpose at all, other than to prove he is "the greatest of deceivers", I guess? This is not a god we should be putting our faith into.