Chef & Friends is completely free to download.
However, the game does offer in-game purchases. These purchases are not essential to progress through the game, but they can be used to improve some aspects of the gameplay.

You can easily manage your ability to make in-game purchases, add a password as a protective measure, or turn off in-game purchases completely using the general settings of your device. The means of doing this depends on your device.

Here are some instructions that may be useful:
• Apple technical support: https://support.apple.com/en-us/102470 
• Google technical support: https://support.google.com/googleplay/answer/1626831?hl=en