Restore Grub Arch based

#Use mhwd-chroot
check partition arch based use gparted

or lsblk -f

#install chroot

yaourt mhwd-chroot or yaourt -S mhwd-chroot-extended

sudo mhwd-chroot-shell

sudo su

lsblk -f

#choose partition arch based

example on sda1

mount /dev/sda1 /mnt

##(note) or use boot partition

mount /dev/sda1 /mnt/boot

#change root

cd /mnt

mount -t proc proc /mnt/proc
mount -t sysfs sys /mnt/sys
mount -o bind /dev /mnt/dev
mount -t devpts pts /mnt/dev/pts/
chroot /mnt

#Restore GRUB

pacman -S mtools os-prober

##For BIOS Systems

grub-install /dev/sda

update-grub

##For UEFI Systems
Create the /boot/efi directory

sudo mkdir /boot/efi

Mount the EFI partition as /boot/efi
example sda1

sudo mount /dev/sd1 /boot/efi

#Re-install Grub

sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=manjaro --recheck

sudo update-grub