Do less sleep can damage the brain? or is too much sleep good for memory? What key lies in sleeping better?

If I wake up after 4 - 5 hours of sleep for going to the toilet or feeling cold or any other reason or for apparently no reason, I can't get back to sleep. I can go to sleep again if I have had 3 hours or less of sleep. I can work if I get up but after completing breakfast at around 8 AM, I have to take to bed. Even then, I can't always sleep. My head aches severely without 7.5 to 8 hours of sleep, the extent of severity depending on the extent of sleep shortage; I also get irascible, my eyes irritate and I make wrong decisions. Incidentally, I am 59, am suffering from IBD, have high myopia and glaucoma but no other serious diseases. If I get to sleep 8 hours a day, I can work as well as I did when I was 25 years old and better than and more than most 25 year olds. However, I get this sleep only 2 - 3 days a year; the result is low productivity.

My son, 18 years old is sleeping only for 4-5 hrs daily ( 12am to 5 am). Is it ok in long run? He is a college student and spends time on gym and studies.

How many hours sleep is recommended daily? Can we compensate if we sleep less lne night by sleeping a lot more the next day? Can sleep cause acid reflux?

how avoid day sleep