Extending root partition - Ubuntu

Currently using Ubuntu 20.4.

I have set up a VM within VSphere. This was initially set with 80GB of HDD. When I booted the VM it showed 'sda - 80GB' with 'sda2 - 40GB'. So I think this is so that it only uses a portion of the hard drive so that it doesn't lock all of the storage into one partition.

Then I though this is easy enough to do I will just run a lvextend. When I run it it says logical volume name "" meaning empty string is invalid. Not sure why though. Plus I cannot run PVS VGS LVS and not sure if this has something to do with how the partitions were originally setup.

Can anyone guide me please. Any help much appreciated on this. Thank you in advance.

Curently what I have done

Your system does not appear to be making use of lvm as indicated by references to /dev/sda2 in the df.

There is not enough data to know for sure - and be aware there is some risk with block operations so back up first, but its likely that either the second partition is oy 40 gigs and needs to be resized (eg with fdisk/parted/gparted) or that the partition is indeed 80 gigs but the filesystem has not been grown - which you can lolely fix with resize2fs or resizefs (same program).