How do i check if my npc is dead? I tried alot of things but none worked

This should work, I'm pretty sure the died function isn't deprecated.

local character = script.Parent
character:WaitForChild("Humanoid").Died:Connect(function()
print(character.Name .. " has died!")
end)

You need to use HUMANOID.Died

here is page on wiki: Humanoid.Died - Wiki

Here is a example:

local npc_humanID = script.Parent:WaitForChild("Humanoid")

npc_humanID.Died:Connect(function()
    print("The npc " .. script.Parent.Name .. " died!")
end)

for play cutscene:

local npc_humanID = script.Parent:WaitForChild("Humanoid")

npc_humanID.Died:Connect(function()
    local cutscene = game:GetService("ReplicatedStorage").Cutscene -- Cutscene Location
    for i,v in pairs(game.Players:GetPlayers()) do
        if v.Character ~= nil then
            cutscene:Clone().Parent = v.Character
        end
    end
end)

Hope it helped :)

Errors? tell-me on comments.