There are problems with this update hanging, I attempted to download and install it 3 times from Settings>Updates and all attempts failed so what I ended up doing was to download it directly from the Microsoft website which completed successfully after about 3 hours, basically what the 20H2 update is, is a complete reinstall of Windows 10. If you’re having issues with it hanging, download and install from Windows downloads on the website, it may be the only way to do it at present. If you are not sure of what space you have on your PC, don’t panic, the download process will automatically calculate that, it’s the first thing it does, if there are any other issues detected you will get pop up message boxes telling you.