why am i getting the error "Disconnect is not a valid member of RBXScriptSignal" ?

heya

i wanted to create a text block that appears when a certain character dies,, though ive put it in kinda weirdly..

i want the heartbeat runservice to disconnect when the enemy is killed,, but i keep getting the same "Disconnect is not a valid member of RBXScriptSignal" error when the character does die

print("YES I DO ANYTYING AT ALL HI")

local RunService = game:GetService("RunService")
local Players = game:GetService("Players") 
local open = false
local heartbeathaha = RunService.Heartbeat

heartbeathaha:Connect(function() 
	if workspace.megabob.Humanoid.Health == 0 then
		heartbeathaha:Disconnect(function()
		print("MEGABOB DEAD YES HI")
		local StarterGui = Players:WaitForChild("PlayerGui")
		local ScreenGui = StarterGui.bobquestion1
		local Frame = ScreenGui.Frame
		Frame.Visible = true
		if open == false then
			open = true
			Frame.Visible = true
			wait(4)
			Frame.Visible = false
			ScreenGui = StarterGui.bobquestion2
			Frame = ScreenGui.Frame
			Frame.Visible = true
			open = true
			Frame.Visible = true
			wait(4)
			Frame.Visible = false
			heartbeathaha:Disconnect()
			end
		end)
	else
		print("THIS CODE WORKS CORRECTLY")
		open = false
		local StarterGui = Players:WaitForChild("PlayerGui")
		local ScreenGui = StarterGui.bobquestion1
		local Frame = ScreenGui.Frame
		Frame.Visible = false
		print("THIS CODE WORKS VERY CORRECTLY")
end
end
)

can someone tell me what exactly is going wrong here..? im not the greatest at troubleshooting

The reason for this error is exactly what the error says; the Disconnect method is not a member of RBXScriptSignal. You're trying to use the Disconnect method on the Event itself which isn't a member of that data type.

The Disconnect method is a member of the RBXScriptConnection data type. The RBXScriptConnection, known as the Connection, is an object returned by the Connect method of an Event. This is used to disconnect a function from an Event.

local RunService = game:GetService("RunService")
local heartbeathaha = RunService.Heartbeat

local connection
connection = heartbeathaha:Connect(function() -- Connects the function to the event and returns the connection object.
	if workspace.megabob.Humanoid.Health == 0 then
		connection:Disconnect()
	end
end)

Documentation

RBXScriptSignal, RBXScriptConnection, Disconnecting Functions from Events