The turnaround time for videos will depend on how many videos are waiting in the queue ahead of yours, your teacher's schedule, and how busy they are with tours, recording, life, etc. These factors make a huge difference, but the average time for a video response is 2-3 weeks.
You may only submit one video at a time for your teacher's review. You will not be able to submit additional videos if you already have a video waiting in your teacher's queue. Once your teacher responds with a VE, you'll be able to send them your next video.