Newbie Help Needed - filter data in an array

I have a firebase with a collection in it:

Reviews
Field 1: name (text)
Field 2: taste (number)

I want to build a dashboard where I am able to submit a page parameter on page load called restoid:
Shared with CloudApp
and it will filter the data in the reviews collection based on the page parameter restoid that I am loading with the page - giving me an array with reviews for only one restaurant:
Shared with CloudApp

I then set a page variable called selectedRestoData:
object with two properties: test2 Composer Pro platform...
name
taste

Problem #1 - when I try to “show” the contents of the page variable selectedRestoData nothing shows up: test2 Composer Pro platform...

Problem #2 - my ultimate goal is to be able to show average score for a selected restaurant
so if I have 2 reviews for Resto1
Name: Resto1 Taste: 4
Name: Resto1 Taste: 6

I want to show average score for that Restorant as 5
No idea how to do it tho - no matter what I try it doesn’t seem to work.

Please point me in the right direction.