There are certain rules for listing items and drafting their description. You can find them in Allegro User Agreement and Terms and Conditions of Charytatywni Allegro.
First of all, please remember that transactions are binding. When you list an item on Charytatywni Allegro, you are obliged to sell it to the auction's winner. You cannot cancel your auction (with some exceptions) and you cannot sell your item "outside Charytatywni Allegro".
These are rules worth reading before listing any item: