If you tried to run apt update and you get this error, try the following.
$ apt update E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable) [duplicate]
Kill the process.
$ sudo killall apt apt-get
If that doesn’t work, remove the locked files.
$ sudo rm /var/lib/apt/lists/lock $ sudo rm /var/cache/apt/archives/lock $ sudo rm /var/lib/dpkg/lock*
Run apt update again.