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(it seems the automatic language identification tool isn't working; it might be best to simply manually select the language of the sentences you're adding)

Need native check ~
Should I add a question particle ?

Yep I saw ^^

I'm not native, but I learned Chinese. I think the sentence is correct like this. I heard it before. No question particle needed. :)

Ok, thanks! :)

How should I modify my sentence to put it to the past tense ?

Chinese doesn't have a past tense.
But if you mean the perfective aspect, that should be 为什么你没理我？ if I'm not mistaken.

We couldn't use 了 ?
And youyr sentence means : "Why did you ignore me?" ?

When using 了 in a negated sentence, the meaning shifts from "not" to "not anymore", so 为什么你不理我了？ means "Why don't you pay attention to me anymore?"

Yes, the sentence I posted means that. 不理 / 没理 literally means "not pay attention" in the sense of reacting to a person and listening to him/her. It would be the right sentence in a situation where an angry girlfriend asks this her boyfriend. ^^

Very interesting, thanks :)