I am using Ubuntu 18.04 in VirtualBox, which has been working for 6 months or so. I am now getting problems when trying to boot into Ubuntu. I get an error message as seen in the photo. I've followed posts saying to type fsck/dev/sda1. After doing so I get onto my Ubuntu desktop, but if I try to open an application, the screen freezes and puts me back into the log in screen.
I've made a short video showing all of this: https://youtu.be/o4TlD7i3PD0