Your problem : Virtual Box keeps its folder and settings in your home folder. Delete everything inside the folder.

Uninstall VirtualBox first.

sudo apt-get remove --purge virtualbox 

Run these commands to delete all virtual machines and settings and Virtual Hard Drives:

sudo rm ~/"VirtualBox VMs" -Rf
sudo rm ~/.config/VirtualBox/ -Rf

If you want to install it again. Run this command:

sudo apt-get install virtualbox

Additionally, check:

sudo ps aux | grep -i "vbox"

Kill any “ghost” processes you may think are relevant.

sudo pkill VBox*