How can we validate this idea for a restaurant/bar app?

I'm a software engineer from the Netherlands. A friend and I have an idea for creating a progressive web app for medium-to-large size restaurants and bars. How would we validate if people would use the following app?

Description

This app would serve two different types of users: guests, and restaurant or bar employees. These users would have a different purpose when using the application.

The guest

The guest scans a QR code with the camera on their mobile, which downloads the app from an app store or goes to the restaurant's website (the website and app are the same application). The app is opened and the guest can see the menu, order, and pay for their items. After the payment has been successfully completed, a notification is sent to the restaurant or bar.

Restaurant or bar staff

The restaurant or bar employee can receive orders in the application, and would also have an overview of the payments. When an order is ready to be served, a notification will be displayed to the user. The guest can then see whether the order is being brought to his table or whether the order is ready at the bar.