"Is Overlapping" is a continuous condition. While Sprite4 is overlapping Sprite6, this event will continue to trigger about 60 times per second. So what happens is you are restarting typewriter again and again very quickly.
You need to use "On collision" event instead. "On collision" is a triggered event, it happens only once at the moment of collision. However, with "On collision" you will not be able to use Else. You'll need to find another way to hide those objects.