Hello Kirill, "You don't want something?" Does not make sense out of context. However if the word 'don't' is stressed in this sentence, it is sometimes used to reiterate a question already asked. For example if you ask a person 'Do you want something to eat?' and they give a response that appeared negative but was unclear, you might then say 'You DON'T want something?' to make sure that you understood them correctly. The same with "You do like this?". If you want to emphasise "do" then you would have to use this sentence after you had already asked someone as a checking method. For example, 'I made you a cake but I don't think you'll like it', the recipient of the cake then eats it and enjoys it so you say in a shocked tone with emphasis on the "do", "You DO like this?' These forms are often used in spoken English but only as a secondary check of information. I hope this helps:)