" 我 = I 好不容易 = with great difficult 帮你 = help you 借来了 = borrow 这本书，this book 谁知道 = who could have known 你现在 = you now 又不要了。don't want the book"

I finally borrowed this book for you ,who knows you don't need it now. 我好不容易帮你借来了这本书，谁知道你现在又不要了。 1.好不容易+v.means it's not easy to do sth eg:这件衣服太脏了，我好不容易洗干净它。 2.谁知道...it's often used the beginning of a sentence,it means something beyonded your expectation eg:谁知道他会突然离开。

It took me great efforts to borrow a book for you only to find that you do not need it now.

Traduction: J'ai aidé à emprunter le livre pour vous(d'une manière pas facile), mais je ne m'attendais pas à ce que vous ne voulez pas maintenant. If my French is not correct, correct me please! ;) Merci