Translation:I do not eat fish, what about you?
没 - refers to physical and present negation, even past negation. ex. I don't eat fish (right now, at this meal) 我没吃鱼. 不 - refers to emotional or intentional negation, and might imply future negation. ex. I don't eat fish (because I don't intend/like to because I don't like it or what have you) 我不吃鱼.
No, because you put 'you' twice. "I don't eat fish, do you?" is acceptable though.
As a general rule, I find it better to avoid contractions on Duolingo, even those which are very well stablished. It's a sure thing, a way of never getting dinged for something silly.
It's probably hard and often dubious for Duolingo's contributors to consider carefully and decide what contractions and alternative words/constructions are worth adding as acceptable answers, and moreover to do it separately for every exercise containing a certain word. So, sticking to simple and standard language (remembering that Duolingo adopts American English as its standard, most likely to match the fact that it's the most taught version of the English language throughout the world today) is definitely the best choice for users here.
Also, a second useful general rule is to pick always the first suggestion showed when you hover over a word, it uses to be the most adequate option for that specific sentence.
(But it's actually better not to hover over words at all after having learnt them, so as to avoid words getting weak faster.)
Hope everyone has a nice time learning here!
It should be accepted without the typo notation. Something in Duolingo's automatic system for contractions is amiss here. It's worthy of a bug report. If you come across a standard contraction not accepted, you can always report it. Unfortunately, there's no good way to report things marked as typos that shouldn't be.
了is "le." It does mean completed actions, but it is an aspect marker, not a tense marker. That means that even without it, you could be talking about the past tense (something seen as incomplete or in progress in the past) and with it, you could be talking about the future or present (something that will be complete in the future.) There is not an exact correspondence between 了and past tense, although it often goes along with past tense.
Why doesn't "do you" instead of "what about you" work? even if it's not a literal translation it has the same operational meaning in this context.
Are you claiming it is more tedious to type "do not" (6 keystrokes) than "don't" (5 keystrokes), as if you really cannot be bothered with one extra keystroke? And even though "don't" is already accepted for this answer (the answer is still counted as correct, but you just get the "you have a typo" response), you want the course developers to type all those extra lines of code into the software, just so you can save yourself a single stroke without getting the "you have a typo" response? I mean, fair enough, but for the same number of tedious keystrokes it took you to type out each word of this request, brief though it is, you could have typed "do not" instead of "don't" at least 80 more times.