Fsck
The articles I used are below. In the end what worked was entering this command on the same screen that detected the error (I couldn't get root access as suggested on the first link).
initramfs: fsck -yf /dev/sda5
https://askubuntu.com/questions/885062/root-file-system-requires-manual-fsck
https://unix.stackexchange.com/questions/479859/ubuntu-recovery-says-fsck-from-util-linux-and-exits
