Definitely you can translate our plugin to your language. Please follow following steps to translate all the strings into french language.
1. Please create a copy of youzify/languages/youzify.pot with your language. For example, if you want to translate it to France, so you need to rename the copy file to youzify-fr_FR.po and youzify-fr_FR.mo.
You can check the list of language code here >> https://wpastra.com/docs/complete-list-wordpress-locale-codes/
2. Open this copied file using POEDIT editor and change language for strings you wants. You can edit it using your text editor as well.
3. Once you are done, click on “Save” and it should generate youzify-fr_FR.mo file on its own.
4. Now upload both the files in languages folder i.e. wp-content/languages/.
5. You should see the language change as soon as you upload it.
Let us know if you have any further query.
Don't forget to clear your browser and site cache after re-upload them.