Record: How to change Firefox menu language

The following site explains how to change Firefox language from one to another
https://support.mozilla.org/en-US/questions/1018686

Steps:

1) on url, type "about:config" (without quote)
2) type "intl.locale.matchOS" (without quote)and set the value to "false"
3) download language pack (up to you)
4) type "general.useragent.locale" (without quote); double click and then change the language type code