That looks great for your first UI design. I would say you make the drop shadow not so thick for the twitter icon as well as the base of the UI. Also, maybe change the font and work on the spacing of the UI. Additionally, I would suggest you make the “X” smaller on the close button of the UI as well.
Overall, that’s a great UI for your first user interface design though with some more work put into the UI, it will look better.