Could not get lock ?

What to do ?
Wait - for what ?

" is another process using it? "

I do not know , if it is what can it be done to stop it ?

Code:a@a-desktop:~$ sudo apt upgrade
E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?
a@a-desktop:~$