Maintaining translations is really painful. I've yet to find a project where it's an easy and painless process. Until now, to translate Monica, you needed to clone the repository, update the language file and finally submit the result as a pull request. Well, no more.
Thanks to Crowdin and their generous open source program, you can now use a very simple tool to translate Monica in the language you want. The project is available at https://crowdin.com/project/monicahq and will ask you to create an account if you want to contribute. Don't hesitate to create an issue if you want to translate a language that we don't support yet.