Problem erasing Mac

RustyMuller wrote:

I have been told to erase my computer. The instructions says: "After the erase is done, select any other internal volumes in the sidebar, then click the delete volume (–) button in the toolbar to delete that volume." But the only volume left is macOS Base System. And I don't know how to go on with erasing the Mac.

the base system is the recovery volume.

Sounds like your drive is failing or need to be repaired.

Disk Utility User Guide for Mac - Apple Support

Solve problems with a disk using Disk Utility on Mac

If a disk in a disk set on Mac fails or is missing - Apple Support

You give no background on the initial issue to begin with... it is very hard to speculate on the backstory here.

You give no corroborating information—

who "told to erase my computer"

what exact mac?

erased how?

You can always Call Customer Support (800) MY–APPLE (800–692–7753)

or on line Apple Support

In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test /assessment

Make an appointment for a "hardware issue"

Genius Bar Reservation and Apple Support Options - Apple

Outside the USA

Find Locations - Apple

RustyMuller wrote:

Thank you for quick answer. The background is that I contacted Mac support because the HD was almost filled - nor with documents - but “other”. The support told me to erase the HD. Now I’m about to reload Big Sur but I’m not sure it is working. One hour left…! :)

I would let the install complete.