I can't go any faster.

我不能走得更快了。

I can't remember the combination.

我不记得密码锁的数码组合了。

I can't stand his brother.

他弟弟让我受不了。

My mum says I can't go.

我妈说我不能去。

I can't make it， unfortunately.

很遗憾，我来不及。

I can't possibly tell you that!

我绝不会把那件事告诉你的！