"Who did you meet there?"
Translation:Kivel találkoztál ott?
I think, it should be WHOM, not WHO. Maybe: (With) whom did you meet there?
You are "correct", it should be whom. But in English today, the accusative whom is dying. Almost everyone uses who now, not whom.
whom is mostly used now, only when 100% formal correctness is needed.
I think, it is much easier to learn and understand a language in the most correct Version, especially for all learners, who learn hungarian or other languages through english, which is not their mother language. Many of us were never in Amerika and we don't know, how the language changes.
If whom is not accepted - report. Otherwise... well you can't force the correct version on half of the world ;-)
-vel means with. But because the v assimilates with a consonant that precedes it, it tends to hide in words e.g. ezzel = with this, a lánnyal = with the girl, a fiúkkal = with the boys, etc.