Why does my health bar script break, and not work well?

I'm not sure what is going on what so ever. (I'm new to coding so excuse the messiness) Ok so, I have a health bar that decreases according to a dummy's health. For some reason, it is always laggy and never consistent. It also breaks every now and then. Here is my code for the dummy health bar.

wait (.1)
local visible = script.Parent.Parent.Parent.Visible
local bframe = script.Parent.Parent.Parent.Parent
while true do
	local hp = game.Workspace.Dummy.Humanoid.Health/500
	script.Parent:TweenSize(UDim2.new(hp,0,1,0),Enum.EasingDirection.Out,Enum.EasingStyle.Quad,0.15)
	wait (0.1)
	if hp < 0.001 or hp == 0 then
		bframe.BaseFrame.Visible = false
		wait (7)
		bframe.BaseFrame.Visible = true
		script.Parent:TweenSize(UDim2.new(0,647,0,70))
		script.Parent:TweenSize(UDim2.new(hp,0,1,0),Enum.EasingDirection.Out,Enum.EasingStyle.Quad,0.15)
		local hp = game.Workspace.Dummy.Humanoid.Health/300
		script.Parent:TweenSize(UDim2.new(hp,0,1,0),Enum.EasingDirection.Out,Enum.EasingStyle.Quad,0.15)
	end
	wait (.2)
end

if you need more code anywhere let me know. Also here is a link to my game so you can just see for yourself what happens.

https://www.roblox.com/games/659823610/Game-Tester#!/about

thank you, and sorry about how messy the code is. I just need to figure out what is happening for some reason.

You should use the .HealthChanged event of the Humanoid instead of having a while loop, it's much more efficient. Here's an example of how you can use it with your game:

local Dummy = workspace:WaitForChild("Dummy")

Dummy.HealthChanged:Connect(function(newHealth)
	script.Parent:TweenSize(UDim2.new(0,647,0,70))
    script.Parent:TweenSize(UDim2.new(newHealth/500,0,1,0),Enum.EasingDirection.Out,Enum.EasingStyle.Quad,0.15)
    script.Parent:TweenSize(UDim2.new(newHealth/300,0,1,0),Enum.EasingDirection.Out,Enum.EasingStyle.Quad,0.15)
end)