Translation of theme and plugin .po language can easily be made right in the WordPress dashboard. Loco Translate reads the .pot template file, provides you with a solid user interface to locate and translate strings, and compiles the .mo files for you. Sounds confusing. It really is not.
For this site, I’ve translated the placeholder in the comment form below, from “Add Comment” to “Add a comment”.
Extract from WordPress.org
Loco Translate provides in-browser editing of WordPress translation files. It also provides localization tools for developers, such as extracting strings and generating templates.https://wordpress.org/plugins/loco-translate/