Wait wait. So Jung is Young which means Jungen is literally young'un? Hehe ok.
It is all explained in the "tips and notes" (which can be found in the web version; if you use a mobile, you can still use a browser instead of the app). Verb forms change with person and number (just like in English you say "I am", but "you are" and "he is"):
sie sind / Sie sind
Note that the English "you" is represented by three different forms in German:
du (informal singular)
ihr (informal plural)
So "you are" can be "du bist", "ihr seid" or "Sie sind", but not a mixture.