You can see the languages you know by typing the following:
/languages
You can also set the language you want to use by typing the following:
/set_language <language>
<language> is case sensitive. Just type it exactly as you see when you use "/language" and you should be fine.
Currently there is no way to know which language you are currently speaking. So if people do not understand you (they will be told that you say something they don't understand), you'll know why. hehehe