A house has all the same components.
Foundation, walls, and a roof.
So why do you need a plan?
The foundation needs to be strong enough to support the walls. The walls need to be strong enough to support the roof. So once you decide what your house will look like, an architect needs to go back and create a plan to ensure that all of these elements work together and create a stable structure.
Then each trade uses that plan to make sure it fulfills its obligation of the construction process to create the final product.
What's your plan to get new guests into your restaurant and have existing guests come back more often?