Here the "heart" refers to the "mind," that is, to one's desires and thoughts. AT: "for within your mind you invented them" or "for you have made this up in your own imagination" (See: [[rc://en/ta/man/translate/figs-metonymy]])
This is a descriptive phrase that means that they are stopping their work on the wall. AT: "The workers on the wall will stop doing the work" (See: [[rc://en/ta/man/translate/figs-explicit]])
Here Nehemiah requests for God to strengthen him by asking him to strengthen his "hands." AT: "strengthen me" or "give me courage" (See: [[rc://en/ta/man/translate/figs-synecdoche]])