Creating a booking with slots - How to change the status of Availability

[angelomaragno]

I want to create a simple app for internal use. This app will be used at an event for my team, on an iPad, to book clients for my VR activity. 

I kind know what I need to do, but dont know how. I've tried find some solution in the forum, with filter, count, automation but couldnt understand properly how to do it. 

So, I have two spreadsheets. The first one is named "Available Time Slots" and has two columns: "Time Slots" and "Availability". The second spreadsheet, named "Reservations," will have a column "Reserved Time Slot" filled through customer selection from the list Time Slots, along with "Name," "Email," and "Phone."

I want book only one person for slot. As soon a record is added to the "Reservations" spreadsheet the time selected should be unavailable for new registration. Basically just book a time for each person and fill up the basic information.

I guess I need to create an automation or action that change the status of "Availability" to FALSE and somehow create something that will not show this selected time in the list. Whats the best way of doing this? Do I need to add formulas, ref or what? 

Attaching some images.

Don't know if the structure is corrected, is there a easier way of doing it?

Thank you