Build a website or add to existing. Read and write to Google Firebase Database

We have a iOS app that reads and writes data to Google Realtime Database. I need my clients to be able to log in and read and write data via a web page:

We have a Visitor Management system that runs on a iOS app. Guest´s check in and out using a iPad. We have a web page created in WordPress that out customers uses to monitor who is checked in, see and add hosts(employees) and send invites (done by writing to Firebase) We are not 100% satisfied with our current solution, and are considering to redo it. The new site does not have to use WordPress

This is what we are after:
The customer should be able to sign up with their email. This will then be their user in Google Firebase. When they have signed up, we need to somehow activate or confirm the account to prevent spam.
When the account is verified, they should be able to:
-See who is signed in
-Sign out a visitor if they forget (delete from Firebase)
-See hosts/employees
-Add/delete hosts/employees
-Send invitations (done by writing to Firebase)

We also need to set up some cloud functions for automatic deletion after a set time.