Why are there so many faults? I am taking the French course which is a beta version. The percentage of faults in the German course is not much lower. Because my knowledge of German is very much better than of French I can judge how bad the mistakes are. For instance; "Sie sollen die Arbeit machen" is translated into "you should do the work". Not a bad phrase, but unhappily enough the translation of: "Sie SOLLTEN (with extra -t-) die Arbeit machen" The original phrase is to be translated into: "you have to do the work." I know enough German and English to dismiss the nonsense, but there are many out there who depend on the material Duolingo gives. I like the idea and the work invested, but the results make me sad.
@siebolt: EDIT: In my first answer I misread your complaint, sorry about that. 'Sie sollten...' is a polite reminder. But 'Sie sollen' ( 'Sie' meaning 'you') is indeed a stronger demand than 'you should' IF it comes directly from the person that gives you the 'order'. On the other hand, if our boss asked me to inform you that you should do some work for him, most naturally I'd say to you 'Sie sollen das Schreiben fertig machen'. In this case the meaning is more 'The boss asked you to...' than 'you have to' or 'you must'. In general, 'sollen' can be used in a whole bunch of different situations and the meaning depends on context. http://www.duden.de/rechtschreibung/sollen
@siebolt: no, I don't think so. 'sollen' is a quite tricky word since it can have so many different - and to some extend even contradictory - meanings: From a very strong moral obligation 'Du sollst nicht töten' to the expression of very uncertain knowledge 'sie sollen die Abgeordneten bestochen haben' ('corre voce que...')
@siebolt: No, it wouldn't be wrong at all. If your boss comes to you and says 'Sie sollen (gefälligst) arbeiten!', 'you must' or 'you have to' would be totally fine as a translation. The only point I want to make is that - as no additional context is provided - duolinguo's translations are also possible.