If your cup is difficult to remove, relax and take your time, don’t worry! Staying relaxed will help your muscles to ease and your cup will be easier to remove.
Try sitting in a squatting position, and use your pelvic floor muscles (the muscles that you use to stop and start peeing) to gently push the cup downwards. When the stem is low enough to reach, pull down until you can reach the walls of the cup, and squeeze them together to release the suction. If the suction seal is hard to break, use your finger between the cup and your vagina to release, and remove.