My friend made me a custom script?

But when I try to change 'run/' it doesn't work when I change it?

current_map = nil

names = {"iSidersz"}

game.Players.PlayerAdded:connect(function(player)
 for i, v in pairs(names) do
  if v == player.Name then 
   player.Chatted:connect(function(chatmsg)
    if chatmsg:sub(1,4) == "run/" then
     local map = chatmsg:sub(5, chatmsg:len())
     if game.Lighting:FindFirstChild(map) then
      if current_map ~= nil then
       current_map.Parent = game.Lighting
      end
      game.Lighting[map].Parent = game.Workspace
      current_map = game.Workspace[map]
     end
    end
   end)
  end
 end
end)