If there's anything you need, just knock on my door.
有什么需要帮忙的话,尽管敲门来找我。
We must stress that these payment terms are very important to us.
我们必须强调这些付款条件对我们很重要。
would be like trying to meet a friend in London without a pre-arranged rendezvous and absurdly wandering the streets in the hope of a chance encounter.