Did the ancient Hebrews believe in the afterlife?

Answer 1

Yes.

One of the central beliefs of Judaism, as codified by Rambam (Maimonides, 1135-1204), is that the soul continues to exist and is treated in accordance with the person's actions while he/she was alive.

Judaism was the religion of the Hebrews from Abraham onwards.

Our ancient sages emphasized the importance of being aware of this: "This world is a mere entranceway before the afterlife" (Mishna, Avot ch.4).

All outstanding accounts are settled after this life. Some cases illustrate this point, since this entire world wouldn't be enough to reward a Moses or punish a Hitler.

The afterlife is detailed at length in the Talmud. A full 20 pages of Talmud (Sanhedrin 90-110) are given to this subject. The afterlife is also referred to briefly in Torah (Bible) verses such as Genesis 15:15, which states that "You (Abraham) will come to your fathers in peace and will be buried in good (ripe; full) old age." This does not mean merely to be buried with one's forefathers, since Abraham was not buried with them. Such verses are stated many times.

The prophets are more explicit with such references (see Isaiah 26:19, Daniel 12:13).

The Tanakh does not delve into detail of the rewards of the righteous, because other religions could compete with even more poetic promises. Also because belief in the afterlife was shared by all ancient societies and needed little reiteration. See the Kli Yakar commentary to Leviticus ch. 26 for a fuller discussion.

Answer 2

There is no written record that the ancient Hebrews held any beliefs about the afterlife, one way or another. There is virtually no mention of it in the Hebrew Bible.