Here Paul uses a double negative. You can translate this in a positive form. Alternate translation: "I very much want you to be aware" (See: [[rc://en/ta/man/translate/figs-doublenegatives]])
Paul does not want the Gentile believers to think they are wiser than the Jewish unbelievers. Alternate translation: "so that you will not think you are wiser than you are" (See: [[rc://en/ta/man/translate/figs-explicit]])
# a partial hardening has come upon Israel, until ... has come in
This is the mystery that Paul referred to earlier in the sentence. This can be made a explicit. Alternate translation: "This mystery is that a partial hardening has come upon Israel, until the full number of the Gentiles has come in" (See: [[rc://en/ta/man/translate/figs-explicit]])
Paul speaks of "hardening" or stubbornness as if it were a hardening of physical organs in the body. Some Jews have refused to accept salvation through Jesus. Alternate translation: "many people of Israel continue to be stubborn" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "full number" means the amount determined by God. It does not mean all Gentiles. Alternate translation: "until the number of Gentiles determined by God" (See: [[rc://en/ta/man/translate/figs-explicit]])
# has come in
This is a metaphor meaning to be saved or to become a Christian. Alternate translation: "are saved" or "become Christians" (See: [[rc://en/ta/man/translate/figs-metaphor]])