If the video is stopping and starting, it’s because the video is too high a resolution for your internet connection. To correct this, look for the blue rectangle at the start of the video timeline on the player. It’s on the far left. See pic below. With your mouse, hover to the immediate right to it and you will see many different resolutions appear. Click a lower resolution and try it until you find one that works with your internet connection.
If you’d like to speed up or slow the video, you can by adjusting the speed. The speed setting is to the far right of the video to the right of the player setting. It will say 1.00x. Click on that and you will see various speed settings. Some people like to speed through a video first, then watch it at a slower speed later.