This phrase is used here to mark the beginning of a new part of the story. If your language has a way for doing this, you could consider using it here. This can also be translated as "It happened that."
The phrase "which he had made" tells about the "window." Some languages may need to make this relative clause a separate sentence: "Noah had made a window in the boat. It came about after forty days that he opened the window." (See the section on clauses in [[rc://en/ta/man/translate/figs-sentences]].)
## raven ##
a bird with black feathers that mainly eats the flesh of dead animals that it finds
## it flew back and forth ##
This means that the raven kept leaving the boat and returning.
## until the water was dried up ##
This could be translated as an active clause: "until the wind dried up the water" or "until the water dried up." (See: [[rc://en/ta/man/translate/figs-activepassive]])