Hey there sorry for late respnse. Simply change your wp-config DEFINE_LANG section to your language for example it_IT and change your language in to the wp-admin to Italian.
Also there is not it_IT po language included the theme and you should translate the theme languages files to your language. \cosmos\languages\ simply dublicate the en_EN.mo and use poedit and translate it into your language and use it as you own language.
I hope this helps to you. Also We’ve replied your email but I think you’ve never got it.