I can't upgrade my system. Can you help me to solve it?

Hi Michael6161,

Thanks for reaching out to Apple Support Communities.

It sounds like you're looking for help with upgrading the OS on your Mac.

We're happy to assist.

You've posted from the best article to help with updating your Mac: Update macOS on Mac

Should the issue continue, follow-up with the steps in this article: If an error occurred while updating or installing macOS

"Install in safe mode

Install while your Mac is started up in safe mode. To start up in safe mode, determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:

Apple silicon

1. Shut down your Mac.
2. Turn on your Mac and continue to press and hold the power button until you see the startup options window.
3. Select your startup disk, then press and hold the Shift key while clicking “Continue in Safe Mode.”
4. Log in to your Mac. You might be asked to log in again.

Intel processor

1. Turn on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.
2. Release the key when you see the login window, then log in to your Mac. 
3. You might be asked to log in again. On either the first or second login window, you should see ”Safe Boot” in the upper-right corner of the window."

Also, make sure that your Mac is supported for anything beyond OS X El Capitan: macOS Sierra - Technical Specifications

"Mac Hardware Requirements

For details about your Mac model, click the Apple icon at the top left of your screen, choose About This Mac, then choose More Info. These Mac models are compatible with macOS Sierra:

• MacBook (Late 2009 or newer)
• MacBook Pro (Mid 2010 or newer)
• MacBook Air (Late 2010 or newer)
• Mac mini (Mid 2010 or newer)
• iMac (Late 2009 or newer)
• Mac Pro (Mid 2010 or newer)"

Cheers!

Numbers requires Monterey for the current stand alone version.

http://www.icloud.com/ has a limited version of Numbers, which should be able to run fine on Sierra and a compatible web browser. The reason I say Sierra, is that it is the first operating system Apple fully supports multifactor authentication with the iPhone and iPad and the Apple ID accounts when you hit 10.12.4.

If for some reason it doesn't work in Sierra, then there are numerous other Excel compatible spreadsheets like

OnlyOffice which even support El Capitan. What you won't get with OnlyOffice, OpenOffice, Google Docs, or Apple iWork is 100% Word compatibility for writing consistent résumés with sites requiring Microsoft Word résumés. Older releases of Office are available to a point, but only as far back as Microsoft's own licensing server supports it if you haven't already purchased Office. Big Sur is required for Microsoft Office itself for the Mac if not already purchased and installed and maintained with a Clone backup of the system that has it installed.