Let the waters ... be gathered
This can be translated with an active verb. This is a command. By commanding that the waters gather together, God made them gather together. AT: "Let the waters ... gather" or "Let the waters ... come together" (See: rc://en/ta/man/translate/figs-activepassive and rc://en/ta/man/translate/figs-imperative)
let the dry land appear
The water had covered the land. Now the water would move aside and some of the land would be uncovered. This is a command. By commanding that dry land should appear, God made it appear. AT: "let dry land become visible" or "let the dry land become clear" or "let the land be uncovered" (See: rc://en/ta/man/translate/figs-imperative)
This refers to land that is not covered with water. It does not refer to land that is too dry for farming.
It was so
"It happened like that" or "That is what happened." What God commanded happened just as he said it should. This phrase appears throughout the chapter and has the same meaning wherever it appears. See how you translated it in Genesis 1:7.
"land" or "ground"
He saw that it was good
Here "it" refers to the land and the sea. See how you translated this in Genesis 1:4.