Not mount hard drive during initial installation

Hello,

I have a problem with my Debian 10 installation, under the ISO downloaded via the AutoVM site.

Indeed, my hard disk does not contain the number of disk space configured in the offer on the creation panel (80 GB here).

Command return from df -h :

Command return from lsblk :

When I want to add the disk space of sda :

[email protected]:/tmp# lvresize -L +80G /dev/mapper/debian–vg-root
Insufficient free space: 20480 extents needed, but only 0 available

[email protected]:/tmp# resize2fs /dev/mapper/debian–vg-root
resize2fs 1.44.5 (15-Dec-2018)
The filesystem is already 2295808 (4k) blocks long. Nothing to do!

[email protected]:/tmp# mount /dev/sda /dev/mapper/debian–vg-root
mount: /dev/mapper/debian–vg-root: /dev/sda already mounted or mount point busy.

Nothing is available…
How can I make my virtual machine have all the resources allocated? 7 Go being far too insufficient to my server live.

Hoping to be able to correct the problem quickly.
Thanks in advance,
Florian, translated from French.