I'd like to buy an English-Chinese dictionary.
我想买本英-汉字典。
A Hello. Do you speak English?
A 你好。你说英语吗？
B Yes, sir. How can I help you?
B 是的，先生。您需要什么？
A I'd like to buy an English-Chinese dictionary. Do you have any?
A 我想买一本英-汉字典。这里有吗？
B Yes, we have several in stock. Large ones and small ones. If you want pocket-sized, I recommend this one.
B 是的，我们有几本存货。有大的也有小的。如果你要袖珍字典的话，我推荐这本。
A That looks perfect, thank you. I'll take it.
A 看起来非常合适。谢谢你。我就买这本。
B Certainly, sir.
B 不客气，先生。

Notes注释
1 A good thing to buy is a dictionary: a dictionary / a dictionary. You can ask: I'd like to buy an English-Chinese dictionary. / I'd like to buy an English-Chinese dictionary – or a Chinese-English dictionary / a Chinese-English dictionary.
需要买的一样好东西是字典：a dictionary /字典。你可以问：I'd like to buy an English-Chinese dictionary. /我想买一本英-汉字典。或者a Chinese-English dictionary /一本汉-英字典。
2 Dictionaries come in many sizes, large, small and pocket-sized: pocket-sized / pocket-sized, for example. Sometimes a shop assistant will recommend a particular one: If you want pocket-sized, I recommend this one. / If you want pocket-sized, I recommend this one.
字典有多种尺寸，例如大的，小的和袖珍的：pocket-sized /袖珍的。有时售货员会推荐某本字典：If you want pocket-sized, I recommend this one. /如果你要袖珍字典的话，我推荐这本。

Key phrases and sentences
Hello. Do you speak English?
Yes, sir. How can I help you?
I'd like to buy an English-Chinese dictionary.
Do you have any?
Well, we have several in stock.
Large ones and small ones.
If you want pocket-sized, I recommend this one.
That looks perfect, thank you. I'll take it.
Certainly, sir.

你好。你说英语吗？
是的，先生。您需要什么？
我想买一本英-汉字典。这里有吗？
是的，我们有几本存货。
有大的也有小的。
如果你要袖珍字典的话，我推荐这本。
看起来非常合适。谢谢你。我就买这本。
不客气，先生。