Set Language wit WP Connect

I am working on a website that imports posts from a database via WP connect. Now i want to set the language based on a field in the database. I already tried to import it as a custom field with ‘post_lang_choice’ as the custom fields name (that already worked in a similar way with an other plugin, WP Event Manager) and that sadly did not work. So is there any way to set the language as an import from an external source and how would that work?