If anybody in the stadium is willing to sell their ticket, I want to buy it!
Is anybody willing to sell their ticket(s)? If so, I would like to buy it!
Anything selling their tickets? I'll buy them!
ご質問ありがとうございます。
① "If anybody in the stadium is willing to sell their ticket, I want to buy it!"=「誰か、スタジアムの中でチケットを売りたい人はいませんか?もしそうであれば、私が買いたいです!」
② "Is anybody willing to sell their ticket(s)?”=「誰か、チケットを売る気はありませんか?」
"If so, I would like to buy it!"=「もしそうであれば、私が買いたいです!」
③ "Anything selling their tickets? I'll buy them!"=「誰かチケットを売っている人はいませんか?私が買います!」
ご参考までに。