Ubuntu is booting very slowly after dual boot with Kali

Boot from Ubuntu installation media.

Select Try Ubuntu without installing.

Step 1 : Reinstall the Ubuntu GRUB boot loader.

Open a terminal and execute :

sudo mount /dev/sda2 /mnt
sudo mount /dev/sda1 /mnt/boot/efi
for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
sudo chroot /mnt
grub-install /dev/sda
update-grub  
exit

Step 2 : Correct the UUID entries in the fstab file.

Open another terminal and execute :

sudo blkid  

Open another terminal and execute :

sudo gedit /mnt/etc/fstab

Replace the UUID entries of sda1 | sda2 | sda3 | sda4

with those of the output given from the blkid command.

Close all terminals and reboot into Ubuntu operating system.