How many days have passed since you arrived in Japan
and how much longer are you planning to stay?
ご質問ありがとうございます。
・「How many days have passed since you arrived in Japan and how much longer are you planning to stay?」
(意味)日本に来て何日目で、あとどれくらい[滞在](https://eikaiwa.dmm.com/uknow/questions/60687/)するの?
<例文>How many days have passed since you arrived in Japan and how much longer are you planning to stay?// It's my first day here and I plan to leave next Friday.
<訳>日本に来て何日目で、あとどれくらい滞在するの?// 今日で1日目で来週の金曜日に帰国する予定です。
参考になれば幸いです。
How many days have you been in Japan and how many more days do you have left here?
この場合、次のような言い方ができますよ。
ーHow many days have you been in Japan and how many more days do you have left here?
「日本に来て何日経って後何日残ってる?」
英語では何日目という聞き方ではなく、何日経ったかという聞き方をするのが普通です。
同じようにあとどのくらいいるかを聞くのも、あと何日残っているかと聞くと良いでしょう。
ご参考まで!