Nice sentence! It's almost correct. A clearer way to say it is:
A cheetah can run as fast as a car in the city.
Why this is better:
- We use A cheetah to mean any cheetah (this sounds more natural than The cheetah when talking about the animal in general).
- As fast as is the right way to compare speed.
- In the city is a short way to say driving in the city.
For a 5-year-old: "A cheetah can run as fast as a car in the city" means the cheetah runs really, really fast — about the same speed as a car driving on city streets.