You can’t use Quran quotes to discredit the Torah which was written and God-breathed many centuries before the Quran. They did not interpret them as trinity because God’s nature was not yet to be revealed at that time, it was revealed when Jesus was born. The Bible does not tell at first chance that it it the Trinity because Moses was the author of the Book of Genesis and it was not revealed yet to Him (by God),there was still a lot of time for the coming of God. Also, just because Jesus didn’t say He knows Abraham it does not mean it is not true. Jesus did not say many things. Are we going to assume everything that includes then? The word “Lord” exclusively means God in the Bible, angels are never referred to as Lords by Christians. Jesus’ complete Christian name is The Lord Jesus Christ, so He along with the Father are the Lord, and they are always mentioned as that.

In Mark, Jesus refers to the monotheistic nature of God, as there is one God (Lord), but God was revealed in 3 states, still it is one God. Jesus in the Bible says a ton of times He is the Son, why would He just randomly say He is not actually God? He doesn’t, this quote is just about monotheistic nature of His followers.