It was a difficult task but we brought it off.

那是一项艰难的工作，但我们还是完成了。

In fact, to learn with success is not a very difficult task if you follow some basic rules.

事实上，如果你遵循一些基本的规则，成功地学习并不是一件非常困难的事情。

As a ballerina, to embody the duality of the Swan Queen and the black swan can be a fiendishly difficult task.

作为一名芭蕾舞女演员，体现天鹅女王和黑天鹅的二元性可能是一项极其困难的任务。

She's set herself a difficult task.

她给自己安排了一项艰巨任务。

She's set a difficult task for herself.

她给自己安排了一项艰巨任务。