If AcyMailing is not translated in your own language, you can easily add a language file in AcyMailing.
Fist of all, you'll have to go on your AcyMailing configuration -> languages.
If AcyMailing is not translated in your language, you should see a small Add Icon next to your language (only installed languages are displayed on this area so you have first to make sure the language file is installed on your website).