5. We're looking for a part-time salesperson to promote our books to local bookstore.
我们正在寻找一个兼职销售人员以向地方书店促销我们的图书。
还能这样说：
We need a salesperson who can work temporarily to promote our books in local bookstores.
There is a part-time position for salesperson to promote our books in local bookstore.
应用解析：
White Book 白皮书（英美政府关于某一问题的官方报告）；
Yellow Book 黄皮书（法国等政府发表的报告书）；
Book of Books (=Books of God, Good Book) 《圣经》

6. I'm calling in reference to your administrative assistant position.
我打电话来询问有关你们行政助理职缺的事。
还能这样说：
Could you give me some information about your administrative assistant position?
Can you tell me some information about your administrative assistant position?
应用解析：
assistant engineer 助理工程师；
assistant manager 副经理

7. Do you need anyone with a Business English background?
你们需要有商务英语背景的人才吗？
还能这样说：
Do you lack of some employee with Business English knowledge?
Does your company have any openings in Business English?
应用解析：
A pretty business!
好麻烦的事情！真糟糕！

8. We have a position for an interpreter.
我们提供口语翻译一职。
还能这样说：
We need an interpreter.
An interpreter is needed in our company.
应用解析：
need指急需；
requisite指导必需品、对某一特殊目的所不能缺少的东西；
necessity属正式用语，指必要、对不可缺少东西的需要。