data not saving when i play in game?

Error 1

Line 9 Should be :GetAsync(), instead of :SetAsync()

:GetAsync() is to get the stored data for the player.

:SetAsync() is to set the new values for the player.

These aren't really errors, but just tips.

For getting the stats, you don't need to define the value as it's returned as a table, so you would have to index the table if you have multiple values.

And you can add your characterAdded, death stuff in the first player added under the 2nd to last end

This is how I would do it, even though I saw an error and a few improvements.

local dataStoreService = game:GetService("DataStoreService")
local myDataStore = dataStoreService:GetDataStore("myDataStore")
wait(5)

game.Players.PlayerAdded:connect(function(player)

    local leaderstats = Instance.new("Folder",player)
    leaderstats.Name = "leaderstats"

    local kills = Instance.new("IntValue",leaderstats)
    kills.Name = "Kills"

    local deaths = Instance.new("IntValue",leaderstats)
    deaths.Name = "Deaths"

    local data
    local success, errormsg = pcall(function()
        data = myDataStore:GetAsync(player.UserId)
    end)

    if success then
        player.leaderstats.Deaths.Value = data[1] or 0
        player.leaderstats.Kills.Value = data[2] or 0 --// Edited
        print("Data loaded")
    else
        warn(errormsg)
        print("Data not saved")
    end

    player.CharacterAdded:connect(function(character)
        local humanoid = character:WaitForChild("Humanoid")
        local deaths = player.leaderstats.Deaths
        humanoid.Died:connect(function()
            deaths.Value = deaths.Value + 1
        end)
    end)
end)

game.Players.PlayerRemoving:Connect(function(plr)

    local dataToSave = {
        plr.leaderstats.Deaths.Value,
        plr.leaderstats.Kills.Value --// Edited
    }

    local success, errormsg = pcall(function()
        myDataStore:SetAsync(plr.UserId,dataToSave)
    end)

    if success then
        print("Data saved")
    else
        print("Data not saved")
        warn(errormsg)
    end
end)

Hope this helped and worked! From my experience, DataStores have been janky very recently.