How To Properly Use DataStoreService For My Levelling System?

Hello! I've recently been wondering how to properly use the DataStoreService for my leveling system. There are no script errors but whenever I test my game the script doesn't work. I have a gui that display's the players xp and level, but when testing my game the xp and level do not show up, the only thing that shows up is the two blank text labels. Also, the leaderstats do not show up either, it's just a leaderboard that states my username. I am wanting my script to be whenever the player achieves new levels and gains xp in game, whenever they join back later on their level and xp remain just as it was when they left and knowing the errors in my script would help me out a ton. I am just recently getting to learn data storage's and I am currently stuck. Any help is appreciated!!

local DataStoreService = game:GetService("DataStoreService")
local levelDataStore = DataStoreService:GetDataStore("levelDataStore")
local xpDataStore = DataStoreService:GetDataStore("xpDataStore")

function onXPChanged(player, XP, level)
	if XP.Value>=level.Value * 10 then 
		XP.Value = 0 
		level.Value = level.Value + 1 
	end
end

function onLevelUp(player, XP, level)
	local m = Instance.new("Hint")
	m.Parent = game.Workspace
	m.Text = player.Name .. " has leveled up!"
	wait(3)
	m.Parent = nil
   player.Humanoid.Health = 0
end


function onPlayerRespawned(player)
	wait(5)

	player.Character.Humanoid.Health = player.Character.Humanoid.Health + player.leaderstats.Level * 10

	player.Character.Humanoid.MaxHealth = player.Character.Humanoid.MaxHealth + player.leaderstats.Level * 10

end

function onPlayerEntered(newPlayer, player)
	
	local stats = Instance.new("IntValue")
	stats.Name = "leaderstats"
	local stats2 = Instance.new("IntValue")
	stats2.Name = "Tycoon"

   local kills = Instance.new("IntValue")
	kills.Name = "Kills"
	kills.Value = 0

	local deaths = Instance.new("IntValue")
	deaths.Name = "Deaths"
	deaths.Value = 0

   local level = Instance.new("IntValue")
   level.Name = "Level" -- The Name of LV
	level.Value = levelDataStore:GetAsync("Player_"..player.UserId) or 1

   local xp = Instance.new("IntValue")
   xp.Name = "XP" -- The Name of XP
	xp.Value = xpDataStore:GetAsync("Player_"..player.UserId) or 0
	local data
	local success, errormessage = pcall(function()
		data = levelDataStore:GetAsync(player.UserId.."-xp")
		data = xpDataStore:GetAsync(player.UserId.."-level")
	end)
	if success then
		level.Value = data
		xp.Value = data
	else
		print("There was a problem loading your data.")
		warn(errormessage)
	end
	
	game.Players.PlayerRemoving:Connect(function(player)
		local s, e = pcall(function()
			levelDataStore:SetAsync("Player_"..player.UserId, player.Level.Value)
			xpDataStore:SetAsync("Player_"..player.UserId, player.Level.Current.Value)
		end)
		if s then
			print("Successfully saved data!")
		else
			print("There was an error when saving data.")
		end
	end)
   
	stats2.Parent = newPlayer	
	stats.Parent = newPlayer
	kills.Parent = stats
	deaths.Parent = stats
   level.Parent = stats
   xp.Parent = stats

	xp.Changed:connect(function() onXPChanged(newPlayer, xp, level) end)
	level.Changed:connect(function() onLevelUp(newPlayer, xp, level) end)

	while true do
		if newPlayer.Character ~= nil then break end
		wait(5)
	end

	local humanoid = newPlayer.Character.Humanoid

	humanoid.Died:connect(function() onHumanoidDied(humanoid, newPlayer) end )


	newPlayer.Changed:connect(function(property) onPlayerRespawn(property, newPlayer) end )


	stats.Parent = newPlayer

end

function Send_DB_Event_Died(victim, killer)

	local killername = "unknown"
	if killer ~= nil then killername = killer.Name end
	print(victim.Name, " was killed by ", killername)

	if shared["deaths"] ~= nil then 
		shared["deaths"](victim, killer)
		print("Death event sent.")
	end
end

function Send_DB_Event_Kill(killer, victim)
	print(killer.Name, " killed ", victim.Name)
	if shared["kills"] ~= nil then 
		shared["kills"](killer, victim)
		print("Kill event sent.")
	end
end



function onHumanoidDied(humanoid, player)
	local stats = player:findFirstChild("leaderstats")
	if stats ~= nil then
		local deaths = stats:findFirstChild("Deaths")
		deaths.Value = deaths.Value + 1


		local killer = getKillerOfHumanoidIfStillInGame(humanoid)


		Send_DB_Event_Died(player, killer)
		handleKillCount(humanoid, player)
	end
end

function onPlayerRespawn(property, player)

	
	if property == "Character" and player.Character ~= nil then
		local humanoid = player.Character.Humanoid
			local p = player
			local h = humanoid
			humanoid.Died:connect(function() onHumanoidDied(h, p) end )
	end
end

function getKillerOfHumanoidIfStillInGame(humanoid)

	local tag = humanoid:findFirstChild("creator")


	if tag ~= nil then
		
		local killer = tag.Value
		if killer.Parent ~= nil then 
			return killer
		end
	end

	return nil
end

function handleKillCount(humanoid, player)
	local killer = getKillerOfHumanoidIfStillInGame(humanoid)
	if killer ~= nil then
		local stats = killer:findFirstChild("leaderstats")
		if stats ~= nil then
			local kills = stats:findFirstChild("Kills")
         local xp = stats:findFirstChild("XP")
			if killer ~= player then
				kills.Value = kills.Value + 1
            xp.Value = xp.Value + 3
				
			else
				kills.Value = kills.Value - 0
				
			end
			Send_DB_Event_Kill(killer, player)
		end
	end
end

game.Players.ChildAdded:connect(onPlayerEntered)