I installed grub 2 after I finished the install.
then I did
grub-mkconfig -o /boot/grub/grub.cfg
and
grub_bios-install --grub-setup=/bin/true --boot-directory=/boot --no-floppy --recheck /dev/sda
and they did fine too.
after that I rebooted and i got
error: symbol not found.
'grub_divmod64_full'

Entering rescue mode ...

grub rescue>
i removed grub2 by pacman and install it again and I did the process again and I get the same error.
I have no idea where and how to fix it but I know it is something to do with grub mostly.