To wake up feeling refreshed the next morning you need at least 7.5 hours of sleep but you might need at least 8 or 9 hours.
All people are different and require different amounts of sleep so if you're not waking up feeling refreshed then you may need to sleep another hour or so.
Also establish a bed time so that you go to bed at the same time each night and then wake up the same time in the morning.
Make sure you go to bed at the same time each night and always get into bed at the same time.
This way your body gets used to going to sleep at the same time.
You may also need to take some sleeping pills or melatonin or have a nice warm glass of milk.
Make sure your room is dark and maybe even wear a sleeping eye mask to help block out light.