Stops working on server test?

Not just the Gui, either. Basically the whole game.

I am trying to make a health GUI i.e. "79/100".

I have tried following MANY tutorials online and got it to "work," but only when the game is run locally. As soon as I run a test server it completely stops working.

My code is such:

local player = game:GetService('Players').LocalPlayer.Character.Humanoid


game:GetService('Players').LocalPlayer.Changed:connect(function()

	local redzone = player.MaxHealth / 4
	if player.Health <= redzone then
		script.Parent.BackgroundColor3 = Color3.new(255,0,0)
	end	

	if player.Health > redzone then
		local brickcolor = BrickColor.new("Lime green")
		local color = brickcolor.Color
		script.Parent.BackgroundColor3 = color
	end

script.Parent.Size = UDim2.new(player.Health/player.MaxHealth,0,0,20)
script.Parent.Parent.hText.Text = (player.Health .. ' / ' .. player.MaxHealth)


end)

I know that this is a VERY basic question and I have spent three days working to solve it, but the resources online are not exactly robust.

edit: sorry for the weird Title, the site wouldn't let me post with my original

Here let me try.

Insert a SCRIPT in the WORKSPACE and write this:

game.Players.PlayerAdded:connect(function(player)
	repeat wait() until player.Character
	local hum = player.Character.Humanoid	
	
	hum.Changed:connect(function()
	
		local redzone = hum.MaxHealth / 4
		if hum.Health <= redzone then
			script.Parent.BackgroundColor3 = Color3.new(255/255, 0/255, 0/255)
		end 
		
		if hum.Health > redzone then
			local brickcolor = BrickColor.new ("Lime green")
			local color = brickcolor.Color
			script.Parent.BackgroundColor3 = color
		end
		
		script.Parent.Size = UDim2.new(hum.Health/hum.MaxHealth, 0, 0, 20)
		script.Parent.Parent.hText.Text = hum.Health.." / " ..hum.MaxHealth
	end)
end)

One of the problem is: Player hasn't got health nor maxhealth. Its humanoid has, tho. So i referred the humanoid. I also used repeat wait() until player.Character (fixes a roblox bug.) I also transformed your not working localscript to a script, which should be working, triggered by playeradded.

If this works, mark this as the Solution, please!

As always, good scripting! :>