What's wrong with my script?

Greetings fellow ROBLOXians
can i get some help on my script?
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player = game.Players.LocalPlayer
mouse = player:GetMouse()

mouse.KeyDown:connect(function(key)
if key == "2" then
player.Character.Humanoid.WalkSpeed = 50
mouse.KeyDown:connect(function(key)
if key == "2" and player.Character.Humanoid.WalkSpeed == 50 then
player.Character.Humanoid.WalkSpeed = 16
end
end)
end
end)
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 "2" = ctrl key when i press the ctrl key my walkspeed will be 50
however when i press the ctrl key again it says like this can i get some he

When you put the key as "2," I think it's listening for the literal 2 number key. Try replacing line 9 on your posted script to if key:byte() == "2" then. That will make it listen for the key whose byte code is 2.