You can pin and delete a card in root but what’s the top button for? The card gets a green border and I don’t find a way to interact with it? What can I do? 
Hello, welcome to the community!
If you’re talking about the option with a plus within four cornered sides of a square, that takes a screenshot of the card itself and saves it in your gallery! I presume the border’s there to let you know that a screenshot was being taken.
You may want to try to check your gallery app to see if there’s a newly-created screenshot of your card.
Hope this helps!