Usually, for experienced users it's ordinary thing to reinstall grub once again but when come to new users it might be complex.

using this shell script shall help new users to reinstall grub it has been tested on ubuntu. It's also support both legacy and efi modes. Please feel free for giving your opinion. Run the script from linux live cd

Official Repository (https://github.com/MohamedElsiddig/grubfix)

#!/bin/bash
###########################################################################
#This Script can help you to fix grub issue after installing windows
###########################################################################

##Written By Mohamed Elsiddig 

################################################################
#The check_efi Function check if there any efi  partition 
################################################################
function check_efi()
{
    echo -e "$light_cyan [ * ]$light_blue Checking for UEFI Instalation$normal " 
    sleep 3
    echo " "
    if [ -d /sys/firmware/efi ] 
        then
            sleep 2
            echo -e "$light_cyan [ * ]$light_blue Found an EFI Instalation$normal " 
            echo " "
            efi_mode=true
            echo -e "$light_cyan [ * ]$light_blue Please select the EFI partition:$normal "
        echo " "
        select efi_dev in $(sudo fdisk -l 2>/dev/null |grep -i 'efi' | sed -n 's#\(/dev/[^[:blank:]]*\).*#\1#p') 'No uefi'
            do
                if [ "$efi_dev" != 'No uefi' ]
                    then
                        echo ""
                        echo -e "$light_cyan [ * ]$light_blue you have chosen: $efi_dev$normal "
                        sleep 3
                        echo ""
                        break
                    else
                        echo ""
                        sleep 3
                        echo -e "$light_cyan [ * ]$white It seem's that your boot media booted in EFI mode but no\n\t EFI partion was selected please create an efi partion and try again ..\n$normal "
                        sleep 2
                        echo -e "$light_cyan [ * ]$white Please refers to this link to learn how to create an EFI partion\n\t https://help.ubuntu.com/community/UEFI ..\n$normal "
                        sleep 2
                        echo -en "$red [ X ] Grub Re-Installation Aborted ..\n\n$normal"
                        exit 1
                fi
            done
        else
            sleep 3
            echo -e "$light_cyan [ * ]$light_blue No UEFI device.. Using legacy mode..$normal "
            efi_mode=false
            sleep 2
    fi


}

#########################################################################
#The part_find Function find the partition that contained the distro
#########################################################################

function part_find()
{
    echo ""
    echo "Checking For Any Linux Installation in the Hard Disk ...!!"
    echo ""
    sleep 1
    for partition in $(fdisk -l 2>/dev/null |grep -i 'linux' | grep -iv 'swap' | sed -n 's#\(/dev/[^[:blank:]]*\).*#\1#p')
        do 
            echo -e "$white Checking $partition$normal"
            mount $partition /media/ > /dev/null 2>&1
            if [ -d /media/boot/grub ]
                then 
                    sleep 2
                    echo -e " $light_green[ ✔ ]$normal$white Found a linux distro in $partition Proceeding with installation"
                    umount /media/ > /dev/null 2>&1
                    sleep 1
                    echo -e " $light_cyan[ * ]$light_blue Operating on $white$partition$normal"
                    sleep 3
                    echo ""
                    grub_fix
                else 
                    sleep 2
                    echo -e " $red[ X ]$white Nothing Here Moving To The Next Partition ...!!"
                    umount /media/ > /dev/null 2>&1
                    echo ""
            fi
    done 
}


################################################################
#The Check Root Function Check For the Root Privilege
################################################################

function chk_root()
{
    if [ $(id -u) != 0 ]
        then
        echo ""
        echo -e $red [x]$cyan::[$red You are not root $cyan]: You need to be [$red root $cyan] to run this script.$normal
        echo ""
        sleep 3
        exit 1
    fi
}


###################################################################
#The Grub Fix Function executes commands thats fix the grub
###################################################################



function grub_fix()
{
    sleep 2
    check_efi
    if [[ $efi_mode=fales ]]
        then
            #echo -en "$light_cyan [ * ]$light_blue Please Enter the target os partition:$normal "
            #read partition
            if [[ ! -d $partition && -e $partition ]]
                then
                    echo -en 
                    mount $partition /mnt
                    for fs_mount  in /dev/ /proc/ /run/ /sys/ 
                        do
                            echo " "
                            echo -e "$orange [ ☣ ]$normal$yellow Mounting $white$fs_mount$yellow Virtual File System ..."
                            sleep 2
                            mount --bind $fs_mount /mnt/$fs_mount > /dev/null 2>&1
                    done
                    echo " "
                    echo -e "$orange [ ☣ ]$yellow Installing The new grub ..."
                    chroot /mnt grub-install "${partition:0:-1}" > /dev/null 2>&1
                    if [ $? -eq 0 ]
                        then
                            sleep 2
                            echo " "
                            echo -e " $light_green[ ✔ ]$normal$light_cyan Installation Complete " 
                            sleep 2
                            echo ""
                            echo -e "$orange [ ☣ ]$yellow Running update-grub ..."
                            chroot /mnt grub-mkconfig -o /boot/grub/grub.cfg > /dev/null 2>&1
                            sleep 2
                            echo " "
                            echo -en " $light_cyan[ * ]$light_blue Do you want to reboot now!! ($light_green yes$light_blue/$red no $light_blue):$normal"
                            read option
                            if [[ ! -z $option && $option = "yes" || "$option" = "y" ]]
                                then
                                echo " "
                                echo -e "$orange [ ☣ ]$yellow Rebooting System ...! "
                                sleep 2
                                reboot
                            elif [[ -n $option && $option = "no" || $option = "n" ]] 
                                then
                                    echo " "
                                    echo -e $orange "Quiting The Script \n" $normal
                                else
                                    echo " "
                                    echo -e $red\"$option\"$normal$orange is not an option$orange "Quiting The Script \n" $normal
                            fi
                        else
                        echo " "
                        echo -en "$red [ X ] Grub ReInstallation Failed !!\n\tTry to execute the steps Manually\n\n$normal"
                        exit 1
                    fi
            else

                echo -e " "
                echo -e $red "[ X ]$normal$white Couldn't Find a linux installation in the Hard Disk !!\n" $normal
                exit 1
            fi
    else
        if [[ ! -d $partition && -e $partition ]]
                then
                    echo -en 
                    mount $partition /mnt
                    for fs_mount  in /dev/ /proc/ /run/ /sys/ 
                        do
                            echo " "
                            echo -e "$orange [ ☣ ]$normal$yellow Mounting $white$fs_mount$yellow Virtual File System ..."
                            sleep 2
                            mount --bind $fs_mount /mnt/$fs_mount > /dev/null 2>&1
                    done
                    echo " "
                    echo -e "$orange[ ☣ ]$yellow Running mount $efi_dev /boot/efi ..."
                    chroot /mnt mount $efi_dev /boot/efi > /dev/null 2>&1
                    sleep 2
                    echo " "
                    echo -e "$orange [ ☣ ]$yellow Installing The new grub ..."
                    chroot /mnt grub-install --target=x86_64-efi --efi-directory=/boot/efi > /dev/null 2>&1
                    if [ $? -eq 0 ]
                        then
                            sleep 2
                            echo " "
                            echo -e " $light_green[ ✔ ]$normal$light_cyan Installation Complete " 
                            sleep 2
                            echo -e "$orange [ ☣ ]$yellow Running update-grub ..."
                            chroot /mnt grub-mkconfig -o /boot/grub/grub.cfg > /dev/null 2>&1
                            sleep 2
                            echo -e "$orange [ ☣ ]$yellow Running umount /boot/efi"
                            chroot /mnt umount /boot/efi
                            sleep 2
                            echo " "
                            echo -en " $light_cyan[ * ]$light_blue Do you want to reboot now!! ($light_green yes$light_blue/$red no $light_blue):$normal"
                            read option
                            if [[ ! -z $option && $option = "yes" || "$option" = "y" ]]
                                then
                                echo " "
                                echo -e "$orange [ ☣ ]$yellow Rebooting System ...! "
                                sleep 2
                                reboot
                            elif [[ -n $option && $option = "no" || $option = "n" ]] 
                                then
                                    echo " "
                                    echo -e $orange "Quiting The Script \n" $normal
                                else
                                    echo " "
                                    echo -e $red\"$option\"$normal$orange is not an option$orange "Quiting The Script \n" $normal
                            fi
                        else
                        echo " "
                        echo -en "$red [ X ] Grub ReInstallation Failed !!\n\tTry to execute the steps Manually\n\n$normal"
                        exit 1
                    fi
            else
                echo -e " "
                echo -e $red "[ X ]$normal$white Couldn't Find a linux installation in the Hard Disk !!\n" $normal
                exit 1
            fi
    fi


}


normal='\e[0m'
cyan='\e[0;36m'
red='\e[1;31m'
green='\e[0;32m'
light_green='\e[1;32m'
white='\e[0;37m'
yellow='\e[0;33m'
light_blue='\e[1;34m'
orange='\e[38;5;166m'
light_cyan='\e[1;36m'


chk_root
echo " "
echo -e "$white [ Tip ]::$cyan To exit press Ctrl C\n$normal"
sleep 2
part_find