Hi Amelia - You can control the closing speed by reducing the duration of the slide layer timelines. They're currently set to 1 second. Try reducing the duration to .5 seconds.
Keep in mind that the slide layer objects (notecard full size) have an entrance animation duration of .5 seconds and an exit animation duration of .25 seconds. You'll need to reduce those times if you shorten the timeline.
Another way to easily speed things up:
1) delete the exit animation effect altogether. Delete the cue point and its associated trigger so the layer fades in and stops at the end of the timeline.
2) change the trigger on the close button. Currently it's set to "resume timeline" when clicked. Change it to "Hide Layer" when clicked. That will make the closing effect instantaneous.