I am using chinese version, but there are some words in the forum frontend not showing the translation properly.
I have checked the chinese translation file, it seems everything has been tranlsated, but it is not showing.
please check the attached screenshot.
it means the phrases are not translated for sure. You should install Loco Translate plugin and check all words.
You can also, use wpForo Phrases to update the not-translated phrases. Go to Dashboard > Forums > Phrases admin page, search that phrases, edit them and change the English word to Chinese. Save it and check again.