I tried to update my "Fedora" by using Terminal. It worked great at first but after a while it said that "there is not enough space in var/". I added some more space by using Gparted and now everything is OK. My question is, How can I clean all useless downloaded files or junk files in var/?
Thank you for your help.

The tail of error was this
" installing package fedora-chromium-config-1.1-3.fc31.noarch needs 81MB on the /var filesystem #Error Summary

**Disk Requirements: At least 81MB more space needed on the /var filesystem."

These are in var/

account crash ftp lib log nis run www adm db games local lost+found opt spool yp cache empty kerberos lock mail preserve tmp

These are in cache/

abrt-di cups foomatic gdm ibus ldconfig libX11 PackageKit realmd app-info dnf fwupd httpd krb5rcache libvirt man private