laptop does not shut down or sleep properly

I'm using a dell

i used this laptop for about one year with windows 10 x64. worked perfectly, nothing to blame

last week i decided to completely reset it. downloaded a windows 10 iso from microsoft and put it on a flash drive, booted from it and deleted everything from my hard drive. i deleted every partition then i made a new one

clean instalation, no problems

my laptop had the a09 bios untill that date. i went on the dell site to download the remaning drivers that weren't installed by windows update and it recommended me to also install the a12 bios

i installed everything and since then i started having these problems

if i turn on the laptop and use it for only 30min-1 hour, it goes normally into sleep and it also shuts down normally. but if i use it for 2-3-4 hours, wheneveer I try to turn it of or put it into sleep it doesn't work. more explicitly, (in the chase of shutting it down) windows closes all applications, the screen goes black, the hard drive activity led flashes, then turns on for 2-3 seconds then it goes out like the os is shut down, but the power button still remains lit and the same with the power on led from under the screen.

hope i will fiind solution here