Dear Mr. Brown,
亲爱的布朗先生，
I have got back home this night, and now I would like to show my thanks for your help during my stay in America.
今天晚上我已经回到家了，现在我想要对你在我美国期间的帮助表示感谢。
I really had a happy learning life. Thanks again.
我真的度过了开心的学习生活。再次谢谢你。

I am sorry to say that I have left an English dictionary there, which means a lot to me. It is a priceless gift from my American teacher.
我很抱歉我落了一本英语词典在那里，它对我很重要，是我一位美国老师送给我的珍贵礼物。
It will be appreciated if you can find and send it to me.
如果你能帮我找到它并寄给我，我将万分感激。
I guess it may be on the bookshelf in the room I stayed before. By the way, I will pay the postage fee.
我猜它可能在我之前住的房间的书架上。还有，我会负责邮费的。
Yours sincerely, Fay
费尔