does it take over 9 hrs to install the macOS Big Sue

Some further thoughts. The download can take 45 minutes to an hour or so, followed by the installation which can take another 45 minutes or so, with several automatic restarts. Your earlier download likely got hung up because of corruption. I'll bet you were using Wi-Fi. Don't. It is too slow for these very large files. Instead, use a wired Ethernet cable. I hope it goes well for you.

Nurse229 wrote:

does it take over 9 hrs to install the macOS Big Sue

At least 45 minutes.

Reboot and see where it leaves you—if it has been hours and hours.

How to upgrade to macOS Big Sur

Big Sur states that you will need 35.5 GB of free storage when upgrading from High Sierra or newer, and 44.5 GB when upgrading from an older versions.

Which OS was your mac running before you tried upgrading to Big Sue.