Paul makes it clear in Romans chapters 9-11 the Jews were cast off. Those Jews in Acts 2 to whom Peter preached the first recorded gospel sermon were lost, NOT OF GOD. Yet those few Jews (”remnant” as Paul calls them in Rom 11) that believed, repented and were baptized became Christians, God’s chosen and had their sins remitted (saved). All the rest of those Jews remained lost for they rejected Christ and His NT gospel in unbelief.
The OT promises made to fleshly Israel have been fulfilled.
The idea fleshly Israel is still God’s chosen comes from the non-Biblical, man made idea of Premillennialism.