We believe that Jesus is a God
You imply there is more that one God. God, Jesus, and the Holy Spirit, three in one.
Muslims get confused about this because of the false doctrine of the Trinity that many Christians profess to believe. It isn't that Christians perceive themselves as worshipping more than one God but rather that those Christians holding to that doctrine have an innacurate perception of God. Fortunately God has been understanding about this even though He doesn't like the false doctrine and doesn't want His name attached to it.
The Father is God, Jesus is God and the Paraclete is God, one spirit in the semblance of three persons but in essence one person.