Well , I know all the good reasons why I should protect my system with password , but I really want to keep using my PC without that popup window asking for password . So I did some searches with DDG and followed some these instrutions:
Terminal commands: explained in that answer
sudo visudo
, editing that file by addingNOPASSWD
in two lines.Then , I followed that answer to make my password empty. After that , I restarted my device but couldn't install any apps from Ubuntu Software centre !!