And you are thoroughly confused if you think Israel was cast away and the Gentiles favored over Israel. You need to read the following chapter IN ITS ENTIRETY though I think it will only confuse you even more than you already demonstrated that you are. Read this chapter VERY CAREFULLY.
As i said the physical tribes were broken off for disbelief and disobedience.
11:17 And if some of the branches be broken off, and you, being a wild olive tree, were grafted in among them, and with them partake of the root and fatness of the olive tree;
11:18 Boast not against the branches. But if you boast, you bore not the root, but the root you.
11:19 You will say then, The branches were broken off, that I might be grafted in.
11:20 Well; because of unbelief they were broken off, and you stand by faith. Be not high minded, but fear:
11:21 For if God spared not the natural branches, take heed lest he also spare not you.
Then Jerusalem was destroyed in 70 AD. For the past 2000 years all are saved only thru faith in Jesus, including the Jews.
Gal.6:15,16 For in Christ Jesus neither circumcision avails any thing, nor uncircumcision, but a new creature. And as many as walk according to this rule, peace be on them, and mercy, and on the Israel of God.
Phil.3:3 For we are the circumcision, which worship God in the spirit, and rejoice in Christ Jesus, and have no confidence in the flesh.
1 Peter 2:9 But you are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that you should show forth the praises of him who has called you out of darkness into his marvelous light; Which in time past were not a people, but are now the people of God:
There are no contradictions where some passages say the Gospel went to the Gentiles as the tribes were broken off and Temple destroyed while other passages say the Jews remain chosen. It does not exist.
Christians are spiritual Israel, the church body, and bride of Christ.