There will be a Preparation Counter, a Oven & a Stove, so your Chef can cook. Chefs take one incomplete order from an Order Stand, complete that order, and repeat the process.
As a chef levels up, it can cook faster, and its plate color changes to silver at level 11, and gold at level 14, which also comes with a price increase.
The max level for a Chef is 15, just like a Waiter.
When hiring a chef, initially, they are not able to cook. In this state, each time a dish is cooked (You have to cook the meals), they will watch and their experience will increase. When it reaches a full bar at 5 meals, it will become a normal chef and is able to cook by itself.