Oh, I am sorry for misunderstanding!
I have to say that the reviews can be displayed only in the original language, and, unfortunately, can’t be translated.
The Language setting changes the language of the widget elements, but not the review itself:
I cannot but agree that this functionality would be of a great value and we have such a request in our Wishlist. You can vote for this feature to receive updates on its development 
Please let me know if this clarifies things or if you have any further questions.