I'm trying to download the Mac OS 11.0 version on my macbook air and I'm having a hard time . Please help

Hi philippeverono,

What year was your MacBook Air made in? You can check by providing your serial number on Apple's Check Coverage page: Check Your Service and Support Coverage - Apple Support

macOS Big Sur 11.0 was never released to the public as an installer - it was the initial macOS version supplied with the M1 MacBook Air, Mac mini, and 13" MacBook Pro.

macOS Big Sur 11.0.1 was released to the public as the first version of Big Sur. Apple's servers no longer provide the macOS installer for this version, but they do provide the restore (IPSW) file for Apple silicon Macs.

The latest version of macOS Big Sur (currently 11.7.9) is available from Apple here: How to download and install macOS - Apple Support (CA)

NOTE: macOS Big Sur will soon stop receiving updates. If your Mac supports a newer macOS version, you should update to that instead (such as Monterey or Ventura).

You can download old versions of macOS here: How to download and install macOS - Apple Support

"Having a hard time" doesn't tell us anything that we can analyze and respond specifically to. Why don't you tell us exactly what problems you are referring to? What messages do you receive? What year and model Mac do you have? What OS is currently installed? Was the download attempted via Wi-Fi?