"Thank you. You're welcome!"
All of the solutions for "you're welcome" should be shown.
I was trying for Bononvenu or something... If I saw the answer(s) more related to my own, I could learn from my mistake. When I saw it I knew that Nedankinde was a good idea too.
it depends on the situation. for example in case you hand over something and get a "dankon" for it, "nedankinde" is the best word. in a situation when someone has just arrived, you could say "bonvenon", "(vi) estu bonvena" or something like that for the welcoming.
I can't confirm for sure but I believe your sentence is correct. "Nedankinde" means "You are welcome!" As where "Bonvenon" is "welcome". To use "Bonvenon" and choosing to omit "Vi estas" seems fine but adding "Vi estas" should not be wrong. You should report this types of errors for review.
Bonvenon is like welcome to my humble obode, bon.ven.on, bon for good, ven for coming, and on to indicate it's a noun in the acusitive, good comings. Nedankinde is like thankyou, you're welcome, ne.dank.ind.e, ne for no, dank for thanks, ind for required or needed, and e to indicate that it is an adverb, no thanks required.
The -n at the end of bonvenon marks it as accusative, the direct object of a verb. "Esti" is a stative verb, which means it does not take direct objects but rather subject complements.
"Bonvenon" is short for something like "I bid you welcome" or "I wish you welcome" or "I give you welcome". All of these are transitive verbs, which take a direct object.
This is why "Vi estas bonvenon" is wrong.