Hey, for the past weeks i've been working on my first minecraft plugin!

Now i came to make my first GUI and i have a couple of Issues!
First of all, my items are in the GUI 2 times! One time at the Postion where i add the item and 1 time at the beginning of the gui. My second issue is that even if an item (red bed, enchanted book) is not in the GUI it still runs the code!