German Language in the post section

Hello,

I have created a small homepage the first time with the Colorway Theme.

I have one small post section on the site, but even the whole site is in the german language, the post section is in english.

I know there is no language file for the theme (should catched up in a later version).

Now the Question, how can I change the language for my post section without a language file?

Need help urgently!!

Thanks and best regards