1. What can i do. with the stacked keyword on the shadow Card?There are Journeyman cards, as I recall, that you can stack onto the Shadows cards in order to increase the difficulty of the Notice check. In general, if you don't have a card that refers to a Keyword on another card, that Keyword is there for future reference.
2. what means "keep an ongoing Effekt After it is spend" does that mean for Example i could keep being in shadows Even After an attack?You do not "spend" Shadows when you make an attack. There are certain Apprentice attacks (Chaotic Overflow comes immediately to mind) that requires you to discard Ongoing cards in order to power it. The item in question allows you to keep some of those cards in play even when you normally would have discarded them to power the attack card.