How nice to hear from you again.

很高兴再次收到你的回信

Let me tell you something about the activity.

让我告诉你一些关于这次活动的细节

I’m glad to have received your letter of Apr. 9th.[/color]

很高兴收到你在4月9号的来信

I’m pleased to hear that you’re coming to China for a visit.

很高兴得知你将来拜访中国

I’m writing to thank you for your help during my stay in America.

我正写这封信感谢我在美国你对我的帮助