Overtime is time that you spend doing your job in addition to your normal working hours.
He would work overtime, without pay, to finish a job.
为了完成工作,他会无偿加班。
work overtime
If you say that someone is working overtime to do something, you mean that they are using a lot of energy, effort, or enthusiasm trying to do it.
We had to battle very hard and our defence worked overtime to keep us in the game.
我们得奋力作战,为了不让我们被淘汰出局,防守队员拼尽了全力。