If we both agree the Old Testament was not written to us then why are you complaining about it?

No, Jesus Christ is our Sabbath and is the fulfilment of the Old Testament. It is written for us to learn from and track the history of our faith.

Islam is not built around the Abrahamic texts at all. It is full of fabricated legends about Bible characters including Jesus. No historical scholar takes the Quran as a serious source for anything. There is no overlap with Christianity since it denies the triune nature of God, the deity of Christ and the gospel of Christ. They are completely different faiths.

And so is Christianity different from Judaism. We believe no one is righteous and by the works of the law no one can be justified. As Paul puts it in Acts 13 I believe verse 39 (too lazy to verify the verse reference forgive me), He says through faith in Christ a man is justified from all things he COULD NOT BE JUSTIFIFED FROM BY THE LAW OF MOSES. Only belief in Christ's death and resurrection and accepting Jesus as SAVIOUR saves.

Do you now see how the two Abrahamic faiths and Islam are all very different concepts?