The ы has nothing to do with the ь and has his own pronunciation. I'd recommend looking up a tutorial about it from a native speaker. It does sound a bit like an i tho,my teacher always said that it's kind of an i but it's pronounced in the back of your mouth instead of the middle.
because it is an question, not an responding to someone, it is a common gramatic.
I am not affirming nothing there, i am questioning someone.
If it has an Question mark, you put "Are you" first.
Open the first link and you will understand better.
Statement questions are perfectly normal and correct in spoken and written English http://dictionary.cambridge.org/us/grammar/british-grammar/questions-statement-questions-you-re-over-18. "You are Dima?" is a completely correct English question.
Statement questions convey an additional bit of information over asking an "Are you/do you," expressing surprise/disbelief or expectation, depending on context (and intonation in speech). Given that information and the answers here, it appears that I wasn't clear enough in my original question. Let me try again: does translating "ты дима?" as "You are Dima?" express something different enough from the question in Russian as to be incorrect?
you can use a virtual "clavier" on your computer, you will find it in Preference systèmes if you have a Mac. With other comuters also. You display it at the same page that the questionnaire of Duolingo and you can past easily from the Russian to the English (or French or whatever) numeric