This board supports multiple languages and you as the User have the option to select which language you will see.
Select the General Settings in your profile
Select first of all the language you want the forum to be displayed in and then select all languages of which you want the threads to see
I have selected the German AND the English threads, so I see all of the threads in the Forum.
If you select only one of them, you will only see the one in that specific language.