Remove residual configuration files: Go to System –> Administration –> Synaptic Package Manager In the left column of the package manager, select Status, and then check for Not Installed (residual config packages). If this option appears, then you will have to right-click each package individually, and select Mark for Complete Removal. After selecting all the packages, click Apply.

1. Remove isolated libraries: Open Terminal and type…

sudo apt-get install deborphan

sudo deborphan

If it appears you have some isolated libraries, then use the following commands in Terminal to remove them:

sudo deborphan | xargs sudo apt-get -y remove --purge

and then
sudo apt-get autoremove