there is only english and no possibility to add language.

Click Edit and add the translation in the language you want
and then Update

https://www.screencast.com/t/YgArkUDOLk

Posted by: @alvina

Also please click on "Delete Phrase Cache" on the Dashboard > Forums > Dashboard admin page before checking.

Posted by: @alvina

There should not be such an issue, just make sure all caches are deleted properly, press CTRL+F5(twice) on the frontend, and check again.

And I have read https://wpforo.com/docs/root/translation/how-to-translate/ (I dont tried to modify the french pot file)

But my problem in the "phrase" possibiity is somewhere else. And perhaps linked to my {numéro}K issue I dont solved https://wpforo.com/community/how-to-and-troubleshooting-2/issue-with-posts-count/#post-46619

I try to translate into french some english words using admin.php?page=wpforo-phrases, but nothing happen even I rebuid phrases and delete all cache.

There should not be such an issue, just make sure all caches are deleted properly, press CTRL+F5(twice) on the frontend, and check again.

Also please click on "Delete Phrase Cache" on the Dashboard > Forums > Dashboard admin page before checking.

Also please follow this doc on how to translate the wpForo plugin: https://wpforo.com/docs/root/translation/how-to-translate/

For example try to translate "Previous Topic"

Il check in phpmyadmin : there are 2 places where I can find "Previous Topic"

1) wp-options table and into "_transient_wpforo_get_phrases_0d67330e40" a long text I join and nothing about my second language "french" 

2) wp_wpforo_phrases table and here I find My translation

And /wp-content/plugins/wpforo/wpf-themes/classic/phrases.js doesn't include my translation