May I have a disembarkation card?

请给我一张离机卡好吗？

We also hope to expand our business with you.

我们也希望与贵公司扩大贸易往来。

I would like to talk to Mr. Liu.

我想请刘先生来听电话。

Will you please call me back?

请你回我一个电话好吗？

We've only sold our product at trade fairs, not in an on-going sales campaign.

我们的产品只在商展时展售，而没有办促销活动。

To answer the first part of your question, I'd like to say that our studies were very extensive.

你问题的第一部分，我要说的就是我们的研究非常广泛。