How to remove 3D print from plate

Hi,
maybe I’m foolish, but I printed 3 things now and my plate looks nasty as hell. I can’t remove the 3D print from the plate (nor the rest of the print). How do you remove the 3D print? Is the black glued mat removable? I have doubts when I loose that mat one time I’ll never get this back on.

Thanks for help!!