英語以外の外国語で寝言聞いたの初めてで何か新鮮だったって英語でなんて言うの？
母国語以外で寝言言えるようになってみたいもんですね。
回答
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It was the first time I'd heard someone talk in their sleep in a foreign language other than English; it was kind of refreshing.
寝言する = talk in one's sleep (「sleep talk」という名詞はあまり聞いたことないです。普通は動詞で言います。)
回答
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It was my first time hearing someone talk in their sleep in a language other than English, and it was rather new to me.
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Hearing someone talk in their sleep in a language other than English was rather new to me.
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My first time hearing someone talk in their sleep in a language other than English was rather new to me.
rather は「かなり、ずいぶん」の意味なので、rather new で「とても新鮮」ということ。a language other than English で「英語以外の言語」となります。
英訳１：It is/was my first time -ing.は「～するのが初めてです／でした」という意味を表せます。
英訳２＆３：hear someone talk は「～が話しているのを聞く」ということ。
その他の言い方：
- It was my first time hearing someone sleep talking in a language that wasn't English, and it felt so fresh.
- Hearing someone talk in their sleep in a language that wasn't English was a new experience for me.
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