Laptop fails to boot

i installed manjaro 20.0.3 genome version.
after the installation i update the repositories (around 400 number and 900 mb size)
when i reboot my laptop after that process the OS failed to boot.
the dialogue displayed on the screen is is similar like this
boot failed:failed to start network manager wait online service.
i reinstall the os
and i type a command “sudo systemctl disable networkmanage”
taken from internet browsing.
but os booting failed this time also.
the difference was this time there is no dialogue or nothing but a blank screen with a frozen cursor.
i reinstall the os third time now.
i still did not update. iam afraid it will break my system again but i need to update the system for later drives of NVIDIA GPU card.
can you please help me to figure out this problem?
NB: i have another O.S called fedora in my system. but i install both OS in separate manual partitions