These words complete the idea that begins with the word "passed" in verse 17. "became Abraham's possession when he purchased it" or "belonged to Abraham after he bought it"
Here "presence" stands for the people serving as witnesses. Alternate translation: "with the people of Heth watching as witnesses" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Here "sons" stands for those who descended from Heth. See how you translated this in [Genesis 23:3](../23/03.md). Alternate translation: "the descendants of Heth" (See: [[rc://en/ta/man/translate/translate-names]])
This tells which sons of Heth saw Abraham buy the property. See how you translated this in [Genesis 23:10](../23/10.md). (See: [[rc://en/ta/man/translate/figs-distinguish]])