9. Then the salesmen have to refresh themselves frequently since we keep producing new products.
我们不断生产新产品，因此销售人员必须经常更新自己。
还能这样说：
The salesmen have to keep constant refreshing as we always update new products.
It is necessary for the salesmen to refresh themselves with the products being produced continuously.
应用解析：
refresh one's memory 使某人想起
例如：
Just refresh my memory: were you born in York?
请再告诉我一次：你是在约克郡出生的吧？

10. We must accelerate our advertising.
我们必须加快广告宣传的速度。
还能这样说：
We must speed up the advertising.
We must propagate the products in a more rapid speed.
应用解析：
accelerate的意思是：使增速；促进，促使……早日发生；使加速。
例如：
We must accelerate the output.
我们必须提高产量。

11. You won't reach all your potential customers with your present methods.
以目前的方式，你无法触及到所有的潜在顾客。
还能这样说：
If you insist on your current methods, you will never reach all your potential customers.
With the present methods, and you won't attract your potential customers.
应用解析：
have method in one's madness 貌似疯狂而实有理智的行为

12. Salesmen have to attend a refresher course frequently.
销售人员必须经常参加进修课程。
还能这样说：
Salesmen need to review the training frequently.
Salesman has to take part in the training program now and then.
应用解析：
off course 不在规定的过程中；
base course 基层；
be on her course 航向不变；
course of action 做法；行动步骤；
golf course 高尔夫球场