I have not received the textbook, so if possible, I would be grateful if you could extend the deadline for submission of the assignment
この文章が以下のように翻訳されています。
教科書が届いていないので課題の提出期限を伸ばして欲しい ー I have not received the textbook, so if possible, I would be grateful if you could extend the deadline for submission of the assignment
教科書が ー The textbook
届いていない ー I haven’t received / hasn’t arrived
ので ー so
課題の提出期限を伸ばして欲しい ー if possible, I would be grateful if you could extend the deadline for submission of the assignment / would it be possible for you to extend the deadline for submission of the assignment
参考になれば嬉しいです。
My textbook hasn't arrived yet. Is there any way you could give me an extension on my assignment that was due tomorrow?
この場合、次のような言い方ができますよ。
ーMy textbook hasn't arrived yet. Is there any way you could give me an extension on my assignment that was due tomorrow?
「教科書がまだ届いていないので、明日期限の課題の（提出期限を）延期してもらうことは可能ですか？」
to give someone an extension on ... で「人に…の期限の延期を与える」
ご参考まで！
オーストラリア 
カナダ 
