Hi Paddy,
Your code has many Wix Code and Javascript errors. I would recommend starting with Wix Code Basics . You can also play with some of the Wix Code Examples which will let you learn by observing working apps. The tutorial How to Use Code to Let Your Users Search a Collection demonstrates how to perform queries and other database techniques.
A gentle warning: The system you are describing is not trivial and will be a challenge for beginner coders. As you learn, we’ll be here to help you get pointed in the right direction.
If your project is urgent and you won’t have enough time to learn how to build your app, you might want to consider checking out the WixArena - it’s a hub where you can look for Wix Code (and other) experts for hire.
Have fun and good luck,
Yisrael