Learn English – Which one is correct: “what did he do” or “what did he does”

When did you born?

is not a grammatical sentence, because born is the past participle of the verb to bear, whereas you must use the bare infinitive after did.

The verb to bear means to generate among other things, so your question can be correcty asked using a passive form,

When were you born?

which is equivalent to, but much more frequent than, *When were you given birth to?"

If your friend wants to answer this question in a grammatically correct way, they should answer I was born on ...

What did he say?

forms a perfect question.

Natives may not opt for What he said? because it lacks the auxiliary verb 'did'.

To form a perfect question with 'what' here, you need to put a verb (auxiliary).

See there, remove a question mark, and it becomes a sentence

That is what he said.

This is the reason of adding an auxiliary verb.

If you are from an Asian country (especially India), it's okay to form a question like that. Asians understand this as a question. But don't practice it if you want to be good at the language. In India, I keep on correcting others whenever I get a chance! :)