Here "brothers" means fellow Christians, including both men and women. AT: "brothers and sisters" (See: [[rc://en/ta/man/translate/figs-gendernotations]])
To "lose heart" is an idiom that means to get tired, weary, or discouraged. AT: "do not be discouraged" or "do not grow weary" (See: [[rc://en/ta/man/translate/figs-idiom]])
"Word" here is a synecdoche for "message" or "teaching." AT: "if anyone does not obey our instructions" (See: [[rc://en/ta/man/translate/figs-synecdoche]]).