Here "you" and "your" are singular and refer to Aaron. Other occurrences of "you" and "your" are plural and refer to Aaron and his sons. (See: [[rc://en/ta/man/translate/figs-you]])
Being inside the curtain represents being inside the room behind the curtain. Alternate translation: "everything in the room behind the curtain" (See: [[rc://en/ta/man/translate/figs-metonymy]])
This can be stated in active form. Alternate translation: "Any foreigner who approaches must die" or "You must put to death any foreigner who approaches" (See: [[rc://en/ta/man/translate/figs-activepassive]])
What they should not approach can be stated clearly. Alternate translation: "who approaches the sacred things" (See: [[rc://en/ta/man/translate/figs-explicit]])