Paul asks this question to emphasize that when God accepts the Jews, it will be a wonderful thing. You can translate it in an active form. AT: "how will it be when God accepts them? It will be like they have come back to life from the dead ones!" or "then when God accepts them, it will be like they have died and become alive again!" (See: [[rc://en/ta/man/translate/figs-rquestion]] and [[rc://en/ta/man/translate/figs-activepassive]])
Paul is speaking of Abraham, Isaac, and Jacob, the Israelites' ancestors, as if they were the first grain or "firstfruits" to be harvested. He is also speaking of the Israelites who are descendants of those men as if they were a "lump of dough" that they made from the grain. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Paul is speaking of Abraham, Isaac, and Jacob, the Israelites' ancestors, as if they were the root of a tree, and the Israelites who are descendants of those men, as if they were the tree's "branches." (See: [[rc://en/ta/man/translate/figs-metaphor]])
# reserved
The people always dedicated to God the first crops that they harvested. Here "firstfruits" stands for the first people to believe in Christ. (See: [[rc://en/ta/man/translate/figs-metaphor]])