"Does she have duck and soup for dinner?"
Translation:У неё на ужин утка и суп?
If I have understood it well, на ужин is an independent clause that means "for dinner" - literally "in the dinner", so it could be omitted or moved to the end for the sake of clarification, so the sentence we are used to is: "у неё утка и суп (на ужни). As we learned in the genitive section, есть can be omitted in some cases. I'm just a Russian learner and English is not my native language, so if I made a mistake, please somebody correct me.
To clarify the point that chucklenuts7 made, есть indicates existence. If we were asking does she have dinner - У неё есть ужин? - we would use есть. However, in this case, we aren't asking if she has dinner we are asking a question about what she is having for dinner. It is implied that dinner exists, we just want to know what it is. So in this case, we use на instead of есть.
The English sentence is ambiguous, which makes it ill-chosen. One could, I suppose, say she has X and Y for dinner in the sense that she has them in her possession and is going to have them for dinner. But the usual meaning of "have X for dinner" is equivalent to "eat X for dinner". After the event, if you say she "had X for dinner", you are not referring to what she had in stock for dinner but to what she actually ate.
Also, "Ты хочешь пообедать?" This means "Do you want to eat lunch?" Not "what do you want to eat for lunch?".
You'd use the perfective verb here. Using the imperfective doesn't make sense because you're asking "wanting to have lunch" implies one particular time, not having lunch in general. The general question could instead be, "Do you like having lunch?" Ты любишь обедать? In the general sense, not a particular lunch on a particular day.
You usually add "н" to "его", "её" and "их" after prepositions. If those are possessives, "н" shouldn't be added. Overall the rules of this are pretty complex. Here is a list of prepositions that require "н": http://cdn01.ru/files/users/images/71/4c/714cba3e577366b4cfc5182ee7e5f905.jpg In the first column there are those that require it, in the second those where it's optional and in the third those that do not need it.
It could be because the Russian letters Е and Ё are not differentiated in the Romanized Russian alphabet "nee." It should technically be "neyo," but really there is no right way without writing in the Russian alphabet. You really should switch to the Russian alphabet in order to learn the language properly. There are several problems with Cyrillic-to-Latin transliteration. Е/Ё ("ye/yo") and Е/Э ("ye/e") can be confusing when trying to transliterate Russian when all three of them transliterate as "E" in English.
When Russians learn English, they learn it in the correct alphabet. It's ridiculous that Duolingo offers to teach Russian in the wrong alphabet. It doesn't work right anyway. I read a lot if comments about people's "correct" answers in the English alphabet being marked wrong anyway. Just like you can't learn English in the Russian alphabet. Ыт ууд би рыдыкюлас! Or, Ит воулд бе ридикюлоус - even worse!