When will this project BEGIN? (The word "begun" is the past participle.) You could say, "The workers have already begun the project". I agree with Michael. It is more common to say, "when will the project start?". Another more formal alternative would be to say, "when will the project commence?".

Got what u meant... Thanks alot... It was really helpful 🌹🌹🙂👍

I sympathise with your problem. It must be tricky when English speakers, as so often, don't agree or give conflicting advice. I don't agree with your other source, and can find very many exact matches for "be begun" on google - more than two million of them. It is a problem for people trying to help to distinguish between what we ourselves typically say and what is permissible or correct in English. Usually, there are many acceptable and "correct" ways of saying almost anything in English. Some of those are ones we prefer, know better, hear more often - and it's natural to steer learners towards those, perhaps. But in my opinion that should not include telling people things are wrong unless they actually are wrong - and I am aware of no grammar or other rule that your sentence breaks ...

Another native speaker from the USA told me that it is weird and wrong to say "when will this project be Begun?"

I wonder who told you this is wrong ... "Begun" should not have a capital letter, which would count as an error. Both of these seem a little clumsy to me, but not strictly "wrong" for any reason I know of. "Be begun" is less used than "be started", google says. "When will this project start?" seems far more natural to me.