I think you're mentally translating back into Italian, and that's why you're confused. "Useful for me" means I benefit from it. Remember that in English, "to (thing)" means a transit or a direction. I know the bigger picture is far more complex, so it's probably better to accept the phrase as correct - yes, it is correct - and use it, instead of trying to analyse it. Prepositions can end a sentence if the thing which follows the preposition has already been mentioned. Repeating the thing is redundant, and changing the sentence so something follows the preposition looks awkward and fussy. The collocation here is "to work on a project".