Why wont the script fire the event?

You're using a while loop to continuously check their chatbox, however this is inefficient and quite redundant.

You could just simply use the .Chatted event to run a function whenever a player talks, and then compare their message to what you want to say, and such.

I'm assuming you wish for the player "world_kiIIer" to be the only one able to use this.

Note: This should be in a LocalScript located somewhere inside the player, so place it inside of StarterGui as it will be cloned to PlayerGui.

Let's set up our variables:

local rep = game:GetService("ReplicatedStorage")
local remote = rep:WaitForChild("RemoteEvent")
local player = game.Players.LocalPlayer

Now we can use the .Chatted event to wait for a player to speak in chat, and then run the function.

You'll notice msg, we will use this to compare their message.

player.Chatted:Connect(function(msg)

Now, since you only want one person to be able to use this, lets stop running the code if their name is not equal to "world_kiIIer".

if player.Name ~= "world_kiIIer" then return end

Now let's read the player's message, and if it is equal to what you wish for them to say, we can run the code inside.

if msg:lower() == "/goto klep" then
	remote:FireServer()
end

We use the :lower() method to change their message into all lowercase characters, so the code will still run even if they have a mixture of both uppercase and lowercase letters.

If it is equal to the string, then we will fire the event.

Full code:

local rep = game:GetService("ReplicatedStorage")
local remote = rep:WaitForChild("RemoteEvent")
local player = game.Players.LocalPlayer

player.Chatted:Connect(function(msg)
	if player.Name ~= "world_kiIIer" then return end
	
	if msg:lower() == "/goto klep" then
		remote:FireServer()
	end
end)

Read more about the .Chatted event here.

If you have any comments or queries, let me know!

Happy scripting!