This phrase refers to other priests who would serve in the temple under the leadership of Joshua. Alternate translation: "the other priests who live with you" (See: [[rc://en/ta/man/translate/figs-explicit]])
Here the word "sign" refers to something that communicates a special meaning to those who see it. Yahweh speaks of the priests serving in the temple as being this sign that shows that Yahweh will bring his servant.
# my servant the Branch
The word "Branch" refers to a messianic figure that would serve as king over Yahweh's people. Yahweh speaks of this person as if he were a branch that grows out from a tree. Since the word "Branch" is a title, it should be translated with an equivalent word in your language. (See: [[rc://en/ta/man/translate/figs-metaphor]])