'What you did?' is wrong. 'What did you do?' is right. Unlike in Portuguese, Spanish and Italian, it is isn't enough to just change your intonation or add a question mark to turn a statement into a question. English questions need a specific word order. In most cases, this is an inversion of the subject and auxiliary or modal verb. For example, in your question you wrote 'Someone can help me?'. This is also not a correct question. The statement is 'Someone can help me.' To make a question, you need to reverse the order of the auxiliary verb (can) and the subject (someone). The correct question should be this: 'Can someone help me?' When you have a question word at the beginning, the order is this: 1. Question word 2. Auxiliary verb 3. Subject 4. Main verb Here are some examples: What are you writing? What have you written? What will you write? As you can see, the tenses are different, but the order stays the same. When you have a simple tense, where the verb form is only one word and there is no auxiliary or modal verb (like 'are' or 'will') , you need to use the auxiliary verb 'do' or 'did', followed by the base form of the verb: What do you write? (present) What did you write? (past) and if the main verb is also 'do', you have the word 'do' twice: What do you do? (present) What did you do? (past) I hope that's clear.

What is the right answer ? I'm confused "What did you do?" is the right answer.