怎样用英语翻译只有用这种方法，我们才能按时完成任务

We can complete the mission on time only through this way.

Useful this kind of method, we can on time complete the mission

only in this way can we accomplish the task on time

it is the only way that we can finish on time

We can't complete it except by this way

It's the only way for us to accomplish the mission on time.
我这个应该比较地道……