OK -- you said the rest of the disk was not in use, but it is.
> /dev/sda5 1001472 1048573951 1047572480 499.5G 8e Linux LVM
It has an LVM volume in it.
The disk is full. The _real_ question is what is in that LVM volume.
It could be a partition or lots of partitions or part of a volume set
spread across other disks -- LVM can do all of that. It could also be
a single encrypted volume. We can't tell you. Only you can find out
what is in there and decide if you can get rid of it.
> The sda1 partition is nearly full, 1GB left.
Since its total size is less than a gig, I think this is wrong. Maybe 1MB left?
There is an entirely separate question here, too: *how* to enlarge it.
This is a virtual disk. So therefore, it is on a virtual machine,
under some kind of remote hypervisor. What kind of hypervisor? How do
you access it?
I am not very familiar with working with remote VMs. I've done it but
not a lot. so I cannot even say what the normal or standard way of
doing this might be; I don't know.
If it was a _local_ VM and I had access to a graphical console to it,
I'd boot it from a live medium -- i.e. the ISO of a recent version of
Ubuntu -- and use GParted to enlarge the partition. But this may not
be possible for you. As you've not said what the remote system is or
what access you have, we can't advise further.