On a fresh Fedora install, the root file system is very small. To extend it:

lvextend /dev/fedora/root -l+100%FREE
xfs_growfs /dev/fedora/root

If error `xfs_growfs is not a mounted xfs filesystem` try:

xfs_growfs /

Notice, both /dev/fedora/root and /dev/mapper/fedora-root point to the same lvm partition /dev/dm-0, so the first argument could be any of the aforementioned three (/dev/fedora/root, /dev/mapper/fedora-root, /dev/dm-0).

lvextend can also grow the partition by only 10GB
lvextend /dev/fedora/root -l+10G