Translation:Thank you everyone for helping me.
"thanks everyone for helping me" was rejected. I think it's ok, though I grant "thanks" may sound a bit casual whereas 感谢 is more of a heartfelt thanks [but we'd rarely say that in English]
Agreed. Also (to my mind):
I appreciate everyone's help.
I appreciate everyone helping me.
I'm grateful for everyone's help.
I'm grateful to everyone for helping me.
Thanks so much, everyone, for helping me.
Thank you so much, everyone, for helping me.
Thank you everyone for helping me is awkward. I would say "thanks to everyone for helping me" or "thank you all for your help"
I think it's fine with the appropriate pauses: "Thank you, everyone, for helping me."
"帮助" is a noun in this instance. It's being modified by "大家对我", which acts as an adjective phrase, and therefore "的" comes between them.
Your suggestion doesn't sound right to me, but I think you could say "感谢大家帮助我", if you wanted to treat "帮助" as a verb (though I like Duo's sentence better).
I welcome corrections.
I'm a little confused about the structure of this sentence. I would have thought it meant "Thank you everyone for my help." Of course, that does not make sense. But how does "我的帮助" mean "helping me" instead of "my help"?
"对我" means "towards me", so "对我的帮助" means "help to(wards) me", or, effectively, "helping me".
So the question then becomes where the "for" is in Chinese (since it's not the "对"). The answer is that the Chinese is idiomatic, and the translation isn't literal. You can essentially think of "感谢" as as an abbreviated way of saying "I thank you for", "I'm appreciative of", or "I appreciate": "I appreciate everyone helping me".
Oh, so it's like (对我)的(帮助), but I thought it was like 对(我的帮助) and I misunderstood what 对 meant here. I guess now I really can say "感谢你对我的帮助" :)
对我 is literally "to me", so it can be more literally translated as "Thank you, everyone, [for your] help to(wards) me." but duolingo probably thinks the given translation is more idiomatic in English.