You can clear NVRAM by reseating the CMOS battery.

umounting and mounting cmos battery doesnt help

How do you know that it didn't clear NVRAM?  Or how did you check ESCD?

Test your battery to see if it needs replacement.  Alternate process is performing an RTC reset, which may not be available on your machine.

it seems  rtc reset won't be possible

https://www.dell.com/support/kbdoc/pl-pl/000125880/how-to-reset-real-time-clock-rtc-to-recover-your-dell-portable-system?lang=en

i dont know what escd is.

as i said, this article:

https://www.dell.com/support/kbdoc/pl-pl/000124377/

is almost useless for laptops

any ideas?