"You are impossible!"
Translation:Du är omöjlig!
When do you write omöjlig or omöjligt? I thought this sentence was omöjligt as that word was at the end..?
The "T" at the end of an adjective, in this case "Omöjligt", means it can only be used with "Ett" nouns.
"Det är omöjligt" - "It's impossible".
When you're describing a person or an "En" word, then it becomes "Omöjlig".
It has nothing to do with the position it is in a sentence.
I checked "Du är omöjlig" and "Ni är omöjlig" But it was put wrong. Is there a difference between them?
du is used for singular and ni is used for plural. However, some people use ni as a ”polite pronoun”, so Ni är omöjlig should have been accepted (I've added it now).
The 'polite' usage of ni is a bit controversial: most people in Sweden don't do it, and some may be offended by it. But it seems to be quite normal in Finland. See this discussion, including the comments: https://www.duolingo.com/comment/5591933