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?
ps aux | grep -i apt
sudo kill <process_id>
# Check if the process was killed by running the ‘ps aux | grep -i apt’ command. If it is still running, force kill it with SIGKILL signal:
sudo kill -9 <process_id>
# Another, easier way would be to use the killall command. This will kill all the instances of a running program:
sudo killall apt apt-get