How do i make a script that gets EACH part in the game?

You can use the for statement to sort through children of the Workspace pretty easily.

Here's some code that will do what you're asking. I explained everything in comments.

a = game.Workspace:GetChildren() --Gets all of the Children of the workspace, regardless of ClassName.
bricks = 0 --This will change when the script finds bricks.

for i,v in pairs(a) do --Starts a for loop to run through the children of the workspace
    if v:IsA("Part") then --Checks if the Child of the workspace's ClassName is "Part".
    bricks = bricks + 1 --Adds 1 to the brick counter.
end
print(bricks) --When the script is done finding the Workspace's children, it will print the total number of bricks in the output.

Hope I helped!

If you want to get every single object in the workspace, then I suggest this:

local ObjectTable = {}
function GetObjects(Area)
    for _,Obj in pairs(Area:GetChildren() do
        table.insert(ObjectTable,Obj)
        GetObjects(Obj)
    end
end
GetObjects(game.Workspace)

This will make table ObjectTable contain every single object in the workspace. However, if you wanted every PART in the workspace, then you would slightly modify the script, like so:

local ObjectTable = {}
function GetObjects(Area)
    for _,Obj in pairs(Area:GetChildren() do
        if Obj:IsA("BasePart") then --This makes sure Obj is a brick
            table.insert(ObjectTable,Obj)
        end
        GetObjects(Obj)
    end
end
GetObjects(game.Workspace)

Hope this helped!