Sleep can be a bit difficult to catch when there is so much going on in your mind whilst learning so many new things.
Here is my trick: I listen to an audio book I know quite well (so that I don't feel I miss anything if I drift off).
My two favorites are:
The World's Lumber Room, which is beautifully written and read by a lady with a lovely voice. All you ever needed to know about what happens to the world's decaying matter!
The History of Rome Podcast, gripping stories about long dead Romans and their wars, 20-30 mins in length, and there are 179 of them, so you will not run out of soap opera material anytime soon.