en_tn_condensed/neh/06/03.md

I sent a messenger to them

Here (and in verse 4) "them" refers to Sanballat, Tobiah, and Geshem. (See: Nehemiah 6:1)

and I cannot

"and I am unable to" or "and I am not able to"

Why should the work stop while I leave it and come down to you?

This is a statement posed as a question that does not expect (and does not get) an answer. The purpose of the question is to challenge Sanballat. AT: "I will not let the work stop while I leave it and come down to you." (See: rc://en/ta/man/translate/figs-rquestion)