They did not know ... an interpreter between them
This shifts from the main story line to background information that explains why the brothers thought Joseph could not understand them. (See: rc://en/ta/man/translate/writing-background)
An "interpreter" is someone who translates what one person says into another language. Joseph placed an interpreter between himself and his brothers to make it seem like he did not speak their language.
He turned from them and wept
It is implied that Joseph wept because he was emotional after hearing what his brothers said. (See: rc://en/ta/man/translate/figs-explicit)
spoke to them
Joseph was still speaking a different language and using the interpreter to speak to his brothers. (See: rc://en/ta/man/translate/figs-explicit)
bound him before their eyes
Here the people are represented by their "eyes" to emphasize what they see. AT: "bound him in their sight" or "bound him as they watched" (See: rc://en/ta/man/translate/figs-synecdoche)
to give them provisions
"to give them the supplies they needed"
It was done for them
This can be stated in active form. AT: "The servants did for them everything that Joseph commanded" (See: rc://en/ta/man/translate/figs-activepassive)