Warning! /dev/sda is in use.Did you unmount all sda partitions?
Please list partitions (that is lowercase L):
sudo fdisk -l
Then run fsck on partitions other than swap:
sudo fsck -n /dev/sda1
or
sudo fsck -n /dev/sda2
If that still throws the superblock corrupt message then
try running e2fsck with an alternate superblock (replace <device> with /dev/sda1 or sda2):
sudo e2fsck -b 8193 <device>