Technique Builders

Mistakes Correct version
He is a seller: He is a salesperson.
She is a commercial: She is a salesperson.
The employee which I work for: The employee who I work for.
That is the company who I work for: That is the company that I work for.

Writing English Builders

Expressions
Food for thought: Something to think about. The article was food for thought.
Self-fulfilling prophesy: When you think about something and it happens.
Asking for the raise was a self-fulfilling prophecy. He had been thinking about it for weeks.
Twofold: There are two possibilities. The answer was twofold. (threefold, fourfold etc...)
A word of caution: Be careful. A word of caution. Do not quit your job before you have another.
n/a: Not available. (for statistics) The report said the data was n/a or not available.
It stinks: It doesn’t smell good or it is awful. (stink stank stunk) The movie stunk.
Slowly but surely: Steady progress. They wanted to progress slowly but surely.