chef
The German word 'Koch' is used to refer to a professional cook or chef. It is a masculine noun, and its feminine counterpart is 'Köchin'. In a professional kitchen setting, 'Koch' is often used to refer to the head chef or the person in charge of the kitchen.
The cook prepares the food.
In this sentence, 'Koch' is used to denote the profession of a person, similar to how 'cook' is used in English. It is used as a noun in the sentence.
I spoke with the cook.
Here, 'Koch' is again used as a noun representing a profession. The sentence indicates a completed action of speaking with a cook.
The cook is making a soup.
In this example, 'Koch' refers to the person who is in the process of making a soup. It consolidates the idea of 'Koch' representing someone involved in culinary activities.