Sleep aids learning in two very important ways:
1). When you get enough quality sleep, your mind focuses better and thus learns better.
2). While you’re sleeping your brain consolidates your memories; that is to say, organises them, files them away in the right places, and ties them down so they last a long time.
Sleep also plays an important role in the development of procedural memory: the kind of learning in which you learn how to do something (like learning to read and recite in Quranic Arabic!).
We Muslims have the advantage that we can say bismillah before going to sleep, thereby dedicating our sleep to Allah (swt) and asking His blessing.
May Allah (swt) richly bless your efforts to learn and spread the message of the Quran.
Be pious scholars of the Lord because of what you have taught of the Scripture and because of what you have studied. [from Al-Quran, 3:79]