Script does not work with multiple parts and idk what to do, can someone help me debug this?

I tried to use some ways that I thought were correct, but none of them worked correctly.

This is the original script:

local Workspace = game:GetService("Workspace")

-- Part Locations

local ClickPart = Workspace:FindFirstChild("ClickPart") --Touching Part
local ChangingPart = Workspace:FindFirstChild("ChangingPart") --Changing Part

-- Processing Section

   local function changingPartsProperties (Hit) --Creating function [The `Hit` is a parameter which tells us `What touched the part?`
    local Character = Hit.Parent
    local Humanoid = Character:FindFirstChild("Humanoid") --Checking if what hit the part has a humanoid

    if Humanoid then --If humanoid is found then....
        print("Changing Properties")
        ChangingPart.Transparency = 0.5
        ChangingPart.CanCollide = true
    end
end

--Connecting Section

ClickPart.Touched:Connect(changingPartsProperties) --Connecting `Touched` event

And I tried: local ChangingPart = Workspace:FindFirstChild("ChangingPart","ChangingPart2") --Changing Part

And: local ChangingPart = Workspace:FindFirstChild("ChangingPart") --Changing Part Workspace:FindFirstChild("ChangingPart2") --Changing Part 2

But they don't work. I hope someone can help me because I tried my best to debug it.

(Also, the original script does not work if the ChangingPart if it's inside a model. I have no idea how to fix this either and it would be appreciated if I got help but it's not my main concern.)