Having trouble installing macOS big sur

If your Mac is capable of running Big Sur and you have sufficient free space for the installation then try the following:

#1 - boot into Safe Mode according to Start up your Mac in safe mode - Apple Support.

NOTE: Safe Mode boot can take up to 3-5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

#2 - go to the System/Software Update preference pane and begin the download.

#3 - run the installer from the Safe Mode.

I've had better luck from the Safe Mode because I evidently have some 3rd party software that interferes with the installation.

Is this an upGrade from Catalina ???

Does this computer Qualify for the upGrade to Big Sur ?? macOS Big Sur is compatible with these computers

Does this computer have the Required Empty Space as per Apple statement below

If upgrading from macOS Sierra or later, your Mac needs 35.5GB of available storage to upgrade. If upgrading from an earlier release, your Mac needs up to 44.5GB of available storage. To upgrade from OS X Mountain Lion, first upgrade to OS X El Capitan, then upgrade to macOS Big Sur.