Fatigue during the day always depends on too little or poor sleep.

No, but often. Most diseases also lead to fatigue as part of the fight against the disease, i.e. an activated immune system.

Sleep before midnight is best.

The claim was true in the old days – when people went to bed at 8 pm. It's the first 4 hours that are most important, but it doesn't matter when you go to sleep.

You can't make up for lost sleep.

Well, that's exactly what you do. Not in hours, but the recovery value. You sleep deeper and thus faster when recovering from sleep deprivation.

REM sleep is important.

It was believed once upon a time. Today the deep sleep is most important for the biological recovery and day-to-day function. REM sleep is nevertheless important, especially for part of the memory process.

You shouldn't wake sleepwalkers.

Yes you can, but cautiously.

You can learn things during sleep.

No, the brain deals with entirely different things and doesn't have time to receive outside impressions. What it does, however, is to fasten the important things we've learned during the day into memory and clean out the unimportant.

It's sufficient to sleep four hours.

No, the average person needs about seven hours, but some variation occurs. Sleeping as little as four hours for a longer period will leave you seriously fatigued and might have negative health implications.

If you're tired upon awakening you have slept badly.

That's not necessarily true. The deeper you sleep when the alarm goes off the harder it is to wake up, but deep sleep means good quality.