Yes, I’m a native speaker. With “Who needs help in English?” you can’t drop the “who” without correcting the tense on “needs.” So, “Need help in English?” would be the right way to go if you want to shorten it further. That is basically a shortened form of “(Do you) need help in English?”

Well, offering support with English with a grammatical failure just seems rather weird, and seeing it repeated doesn't make it better.

Had you said "Would anyone like help with their English?" or "Do you need help with English?" the repeat would have been acceptable.

I do. And I hope so will most people interested in actually learning English. ;)

"informal" is not an excuse for laziness and poor form, or, as it were, bad grammar.

Point out one question here https://learnenglish.britishcouncil.org/english-grammar-reference/questions-and-negatives that matches your pattern....

You're entitled to that view, I guess. And I have every right not to share it.

To me the title is just poor grammar, and in informal speech it's still pidgin.