Jackie,
I struggle with insomnia on a daily basis. I was once used to getting a lot of sleep, 8 hours or so regularly. Now I manage working with 4-6. It's an ongoing journey. I've done a lot of reading about sleep, meditation, and the intersection between sleep and meditation.
I had a lot of trouble on my course with sleep. It got to the point where I told the AT that I was considering leaving. The idea of getting only 3 hours of sleep a night was really weighing on me psychologically. But the AT told me something that stuck with me: "you're craving sleep. Don't crave sleep." He followed that with "If you told me you weren't sleeping at all, I'd be worried. But three hours is plenty."
I explored that point of view a little. Maybe I didn't need as much sleep as I thought. And sure enough, letting go of the craving was enough to ensure a good sleep that night, better than any night in months. So that was an interesting event that has led to a lot of personal understanding. To make things punchy, it helped me see that when it comes to sleep, the more you want, the less you get. Plus, not all sleep is equal; sometimes I get 6 or even 5.5 really great hours that leave me feeling refreshed, something I could have never imagined before.
Is it possible that you, too, are craving sleep? That the "need" is partly psychological instead of physiological?
You mention a few other things: "I would like to keep up my meditation but I just feel my bodytype just could not stand these courses." "but after the course everyone should feel relieved and happy." "I still need to rest a lot and sleep for about 12 hours daily." "I tried to give my best to make progress with my meditation."
What do these statements have in common? They are judgments and conclusions about you that neither you nor anyone else has the right to make. Who's to say that your bodytype is different from anyone else's? Who's to say that we should all be relieved and happy at the end of a course? Who's to say you really need twelve hours of sleep/rest daily? And finally, is possible that you are trying too hard to make progress?
Finally, some information you may find interesting. It seems like meditation can indeed improve sleep organization, but the effect is limited to senior meditators (practitioners 2+ hours per day, >3 years) , at least in the articles I can find.
Here are a few articles. They're paywalled, but you can use libgen or sci-hub to access them.
https://www.tandfonline.com/doi/abs/10.3109/09540261.2016.1159949https://www.frontiersin.org/articles/10.3389/fneur.2012.00054/fullhttp://www.sleep-journal.com/article/S1389-9457(17)31119-X/abstractTo close: it sounds like you're doing great, and that maybe you want to consider reflecting on potential attachments to sleep, or to ideas you may have about your own limitations. I look forward to reading other folks' opinions.
oscarabeo