How I can save my XP and LVL in this script ?

local Properties = Game.Workspace.GAME_PROPERTIES

function onXPChanged(player, XP, level) 
	if string.lower(Properties.XPType.Value) == "linear" then --Linear (1, 2, 3, 4, 5, etc)(High level cap recommended.)
		if XP.Value>= Properties.XPPerLevel.Value * (level.Value) + Properties.AdditionalXPNeeded.Value and level.Value < Properties.LevelCap.Value then 
			XP.Value = XP.Value - (Properties.XPPerLevel.Value*(level.Value) + Properties.AdditionalXPNeeded.Value) 
			level.Value = level.Value + 1 
		end 
	elseif string.lower(Properties.XPType.Value) == "square" then --Square (1, 4, 9, 16, 25, etc)(Medium level cap recommended.)
		if XP.Value>= Properties.XPPerLevel.Value * (level.Value * level.Value) + Properties.AdditionalXPNeeded.Value and level.Value < Properties.LevelCap.Value then 
			XP.Value = XP.Value - (Properties.XPPerLevel.Value * (level.Value * level.Value) + Properties.AdditionalXPNeeded.Value)
			level.Value = level.Value + 1 
		end
	elseif string.lower(Properties.XPType.Value) == "exponent" then --Exponent (1, 2, 4, 8, 16, etc)(Low level cap recommended. Exponent rate dictated by XPPerLevel divided by 100.)
		if XP.Value>= math.pow(Properties.XPExponentMagnitude.Value/100, level.Value-1) * Properties.XPPerLevel.Value + Properties.AdditionalXPNeeded.Value and level.Value < Properties.LevelCap.Value then 
			XP.Value = XP.Value - math.pow(Properties.XPExponentMagnitude.Value/100, level.Value-1) * Properties.XPPerLevel.Value + Properties.AdditionalXPNeeded.Value
			level.Value = level.Value + 1 
		end 		
	end
end 

function onLevelUp(player, XP, level) 
	if player.Character~=nil then 
		for i = 1,5 do 
			local fireworks = Instance.new("Part") 
			fireworks.Shape = 0 
			fireworks.formFactor = "Symmetric" 
			fireworks.Size = Vector3.new(1,1,1) 
			fireworks.BrickColor = BrickColor.Random() 
			fireworks.CFrame = player.Character.Head.CFrame + Vector3.new(0,2,0) 
			fireworks.Parent = game.Workspace 
			game:GetService("Debris"):AddItem(fireworks, 2) 
			fireworks.Velocity = Vector3.new(math.random(-30,30),math.random(-30,30),math.random(-30,30)) 
		end 
	end 
	local m = Instance.new("Hint") 
	m.Parent = game.Workspace 
	m.Text = player.Name .. " has gained a level!" 
	wait(5) 
	m.Parent = nil 
end 

function SaveData(Player)
	if Player.DataReady == false then
		warn("Could not save, DataReady is false.")
		return
	end
	--Stats
	local Stats = Player.leaderstats:GetChildren()
	for i = 1, #Stats do
		if Stats[i]:IsA("IntValue") or Stats[i]:IsA("NumberValue") then
			Player:SaveNumber(Stats[i].Name, Stats[i].Value)
		elseif Stats[i]:IsA("BoolValue") then
			Player:SaveBoolean(Stats[i].Name, Stats[i].Value)
		elseif Stats[i]:IsA("StringValue") then
			Player:SaveString(Stats[i].Name, Stats[i].Value)
		end
	end
	--Attributes
	local Attributes = Player.attributes:GetChildren()
	for i = 1, #Attributes do
		Player:SaveNumber(Attributes[i].Name, Attributes[i].Value)
	end
	--Armors
	local Armors = Player.UnlockedArmor:GetChildren()
	for i = 1, #Armors do
		if Armors[i]:IsA("IntValue") or Armors[i]:IsA("NumberValue") then
			Player:SaveNumber(Armors[i].Name, Armors[i].Value)
		elseif Armors[i]:IsA("BoolValue") then
			Player:SaveBoolean(Armors[i].Name, Armors[i].Value)
		elseif Armors[i]:IsA("StringValue") then
			Player:SaveString(Armors[i].Name, Armors[i].Value)
		end
	end
	print("Data has been saved successfully for " .. Player.Name .. "!")
end

function LoadData(Player)
	if Player.DataReady == false then
		warn("Could not load, DataReady is false.")
		return
	end
	--Stats
	local Stats = Player.leaderstats:GetChildren()
	for i = 1, #Stats do
		if Stats[i]:IsA("IntValue") or Stats[i]:IsA("NumberValue") then
			local temp = Player:LoadNumber(Stats[i].Name)
			if temp >= 0 then --Prevents the loading of negative stats.
				Stats[i].Value = temp
			end
		elseif Stats[i]:IsA("BoolValue") then
			local temp = Player:LoadBoolean(Stats[i].Name)
			Stats[i].Value = temp
		elseif Stats[i]:IsA("StringValue") then
			local temp = Player:LoadString(Stats[i].Name)
			Stats[i].Value = temp
		end
	end
	--Attributes
	local Attributes = Player.attributes:GetChildren()
	for i = 1, #Attributes do
		local temp = Player:LoadNumber(Attributes[i].Name)
		if temp >= 0 then
			Attributes[i].Value = temp
		end
	end
	--Armors
	local Armors = Player.UnlockedArmor:GetChildren()
	for i = 1, #Armors do
		if Armors[i]:IsA("IntValue") or Armors[i]:IsA("NumberValue") then
			local temp = Player:LoadNumber(Armors[i].Name)
			if temp >= 0 then
				Armors[i].Value = temp
			end
		elseif Armors[i]:IsA("BoolValue") then
			local temp = Player:LoadBoolean(Armors[i].Name)
			Armors[i].Value = temp
		elseif Armors[i]:IsA("StringValue") then
			local temp = Player:LoadString(Armors[i].Name)
			Armors[i].Value = temp
		end
	end
end

function onPlayerEntered(newPlayer)

		--Variables folders
		local stats = Instance.new("Model")
		stats.Name = "leaderstats"

		local attrb = Instance.new("Model")
		attrb.Name = "attributes"
		
		local misc = Instance.new("Model")
		misc.Name = "Stats"
		
		local armor = Instance.new("Model")
		armor.Name = "UnlockedArmor"

		--Leaderstats variables
		local clicks = Instance.new("IntValue", stats)
		clicks.Name = "Lvl"
		clicks.Value = 1

		local clicks2 = Instance.new("IntValue", stats)
		clicks2.Name = "XP"
		clicks2.Value = 0

		local clicks3 = Instance.new("IntValue", stats)
		clicks3.Name = "Gold"
		clicks3.Value = 0

		--Attributes
		local attrb1 = Instance.new("IntValue", attrb)
		attrb1.Name = "Strength"
		attrb1.Value = Properties.StartingAttributes.Value

		local attrb2 = Instance.new("IntValue", attrb)
		attrb2.Name = "Constitution"
		attrb2.Value = Properties.StartingAttributes.Value

		local attrb3 = Instance.new("IntValue", attrb)
		attrb3.Name = "Intelligence"
		attrb3.Value = Properties.StartingAttributes.Value

		local attrb4 = Instance.new("IntValue", attrb)
		attrb4.Name = "Dexterity"
		attrb4.Value = Properties.StartingAttributes.Value

		--Other stats
		local mana = Instance.new("IntValue", misc)
		mana.Name = "Mana"
		mana.Value = 100
		
		local maxmana = Instance.new("IntValue", misc)
		maxmana.Name = "MaxMana"
		maxmana.Value = 100
		
		local equippedArmor = Instance.new("StringValue", misc)
		equippedArmor.Name = "EquippedArmor"
		equippedArmor.Value = "None"
				
		local defense = Instance.new("IntValue", misc)
		defense.Name = "Defense"
		defense.Value = 0
		
		--Unlocked armors
		local unlockedArmorLeather = Instance.new("BoolValue", armor)
		unlockedArmorLeather.Name = "UnlockedLeather"
		unlockedArmorLeather.Value = false

		local unlockedArmorChainmail = Instance.new("BoolValue", armor)
		unlockedArmorChainmail.Name = "UnlockedChainmail"
		unlockedArmorChainmail.Value = false

		local unlockedArmorBronze = Instance.new("BoolValue", armor)
		unlockedArmorBronze.Name = "UnlockedBronze"
		unlockedArmorBronze.Value = false

		local unlockedArmorIron = Instance.new("BoolValue", armor)
		unlockedArmorIron.Name = "UnlockedIron"
		unlockedArmorIron.Value = false

		local unlockedArmorSteel = Instance.new("BoolValue", armor)
		unlockedArmorSteel.Name = "UnlockedSteel"
		unlockedArmorSteel.Value = false

		local unlockedArmorMithril = Instance.new("BoolValue", armor)
		unlockedArmorMithril.Name = "UnlockedMithril"
		unlockedArmorMithril.Value = false

		local unlockedArmorAdamant = Instance.new("BoolValue", armor)
		unlockedArmorAdamant.Name = "UnlockedAdamant"
		unlockedArmorAdamant.Value = false

		local unlockedArmorDemonic = Instance.new("BoolValue", armor)
		unlockedArmorDemonic.Name = "UnlockedDemonic"
		unlockedArmorDemonic.Value = false

		local unlockedArmorBone = Instance.new("BoolValue", armor)
		unlockedArmorBone.Name = "UnlockedBone"
		unlockedArmorBone.Value = false
				
		--PvP		
		if Properties.HasPvP.Value == true then
			local clicksPvP = Instance.new("IntValue", stats)
			clicksPvP.Name = "PvP Points"
			clicksPvP.Value = 0
			
			local inPvP = Instance.new("BoolValue", misc)
			inPvP.Name = "InPvP"
			inPvP.Value = game.Workspace.GAME_PROPERTIES.GlobalPvP.Value
		end

		--Assign the folders to player.
		stats.Parent = newPlayer
		attrb.Parent = newPlayer
		misc.Parent = newPlayer
		armor.Parent = newPlayer

		clicks2.Changed:connect(function() onXPChanged(newPlayer, clicks2, clicks) end) 
		clicks.Changed:connect(function() onLevelUp(newPlayer, clicks2, clicks) end) 

		newPlayer:WaitForDataReady(true) 

		LoadData(newPlayer)

		newPlayer.CharacterAdded:connect(function(c) 
			c.Humanoid.MaxHealth = (Game.Workspace.GAME_PROPERTIES.StartingHP.Value) + (Game.Workspace.GAME_PROPERTIES.HPPerLevel.Value * newPlayer.leaderstats.Lvl.Value) + (Game.Workspace.GAME_PROPERTIES.HPPerConstitution.Value * newPlayer.attributes.Constitution.Value)
			c.Humanoid.Health = c.Humanoid.MaxHealth
		end) 
end 

function onPlayerRemoving(player)
	print("Attempting to save score for " .. player.Name)
	SaveData(player)
end

game.Players.PlayerAdded:connect(onPlayerEntered)
game.Players.PlayerRemoving:connect(onPlayerRemoving)