I highly recommend this short article.  Here is a brief quote:

What’s emerged over the past 20 years has been that, while we’re asleep, we may be immobile, but there’s so much going on within the brain. In fact, so many processes that go on while we’re asleep essentially define how effective we are during the wake state.

https://endpoints.elysiumhealth.com/russell-foster-sleep-tips-2cf047eab286