fast asleep	sleeping in a way that makes it difficult to wake you
fell into a deep sleep	zasnąć głęboko
sleep soundly	sleep well
get a good night's sleep	spać dobrze
sleep rough	to sleep outside because you do not have anywhere to live
wide awake	completely awake
have sleepless nights	mieć bezsenne noce
light sleeper	someone who wakes easily when they are sleeping