en_tn/rom/11/23.md

if they do not continue in their unbelief

The phrase "do not continue in their unbelief" is a double negative. You can translate this in a positive form. Alternate translation: "if they start believing" (See: rc://en/ta/man/translate/figs-doublenegatives)

will be grafted in

Paul speaks of the Jews as if they were branches that could be grafted back into a tree if they start to believe in Jesus. You can translate this in an active form. Alternate translation: "God will graft back in" (See: rc://en/ta/man/translate/figs-metaphor and rc://en/ta/man/translate/figs-activepassive)

graft

This is a common process in which the end of a live branch of one tree is inserted into another tree so that the new branch will continue to grow in that tree.

they ... them

All occurrences of "they" or "them" refer to the Jews.