I run first this command sudo nvidia-installer-dkms -f, and after that i run yay -S nvidia-390xx-dkms but after rebooting i got black screen. I guess i did something wrong but not sure what.
First of all, if nouveau driver works, you could use that during troubleshooting.
If you can use the TTY (press Alt-Ctrl-F2), you can uninstall nvidia drivers (sudo nvidia-installer-dkms -n) and reboot with nouveau.