Bitcoin paper wallet and Bitcoincash withdrawal? Let's say I have a bitcoin paper wallet with a public and a private key, with an amount of X bitcoin on it. On the 25th of November, the hardfork of bitcoin gold will take place, so I will get the same amount of bitcoin gold.

The question is, how I will be able to withdraw only bitcoin gold from that paper wallet as I have only one public and private key as they are bound to a bitcoin wallet?
You will receive an equal amount of Bitcoin Gold as you have in your Bitcoin paper wallet at the time of the fork.  Your paper wallet that contains the Bitcoin will automatically contain the Bitcoin Gold.  In other words, your private key controls both.  We will have to wait to see which online wallets and exchanges support Bitcoin Gold in order to "split" Bitcoin Gold from Bitcoin to be able to withdraw or exchange them.  This is the same scenario as the BTC/BCH hardfork that occurred on Aug 1.