is it possible to uppgrade iMac Quad-Core i5 to version 11.0?

What model year is it? The model year of an iMac is available at Apple menu > About This Mac.

A mid 2014 and late 2014 iMac (or later) can be upgraded to the latest version of Big Sur macOS 11 but no later. 

A late 2015 iMac can be upgraded to the latest version of Monterey macOS 12 but no later. 

A 2017 iMac can be upgraded to the latest version of Ventura macOS 13 but no later. 

For all of the above, see instructions in: How to download and install macOS - Apple Support  

A 2019 or later iMac can be upgraded to the current version of Sonoma macOS 14. See:How to upgrade to macOS Sonoma - Apple Support

The answer is dependent on the model year of the iMac, please let us know that information. If you don't know it is in "About this Mac" which you can find by clicking the Apple symbol in the upper left of the display.

A late 2012 iMac can be upgraded to Catalina 10.15.7 but no later.