"Son of a human being" or "Son of humanity." God calls Ezekiel this to emphasize that Ezekiel is only a human being. God is eternal and powerful, but humans are not. See how you translated this in [Ezekiel 2:1](../02/01.md). Alternate translation: "Mortal person" or "Human"
"to the places under the ground." When people died, they were put in the ground. So "bring them down ... to the lowest earth" means "make them die." (See: [[rc://en/ta/man/jit/figs-idiom]])
"The pit" refers to the grave; because the grave was thought to be the entrance to the world of the dead, the pit also represents that world. See how you translated this in [Ezekiel 31:16](../31/16.md). (See: [[rc://en/ta/man/jit/figs-metonymy]])