When you start choosing to assist others, not because you have to but because you would rather help them because their work is more interesting or engaging than your own work.
2
如果你能明白“专心”的意思,就没问题。
As long as you understand the word "concentration", then yes.
3
在教室里,当你望向窗外或拉别人的头发时,老师会叫你专心,这是什么意思?
In a class room, when you stare out of the window or pull somebody's hair, the teacher tells you to pay attention. Which means what?