Source

 sudo pkcon refresh force -c -1 

 rm -f /var/cache/PackageKit/metadata/updates/packages/*

Disable the saving of the rpm's:
Edit /etc/PackageKit/PackageKit.conf and remove the # of KeepCache

# Keep the packages after they have been downloaded
KeepCache=false 

dnf clean all --enablerepo=\* 

Source

You can delete everything inside of /var/log/journal/* but do not delete the directory itself.

• You can also query journalctl to find out how much disk space it's consuming:

  $ journalctl --disk-usage
  Journals take up 3.8G on disk.

• You can control the size of this directory using this parameter in your /etc/systemd/journald.conf:
  SystemMaxUse=50M
• You can force a log rotation:

  $ sudo systemctl kill --kill-who=main --signal=SIGUSR2 systemd-journald.service 

• You might need to restart the logging service to force a log rotation, if the above signaling method does not do it.
  You can restart the service like so:

  $ sudo systemctl restart systemd-journald.service