How do I make an Item that saves when you die?

how do I make an Item doesn't get taken away when you die?

Every player automatically has a StarterGear container. Any tool parented to here will automatically be given each time the player spawns.

Here's a solution for your problem it is very simple :

-- Variables

local Tool = script.Parent
local Player = game.Players.LocalPlayer
local Backpack = Player:FindFirstChild("Backpack")

-- Creating a function that basically gives the player the tool :

function MoveScript()
	wait() -- Waiting a bit so it doesn't say "Something unexpected tried to change the parent"
	Tool.Parent = Backpack -- Setting the parent to the backpack
end

-- Calling The Function :

MoveScript()