could not install macOs Big

Hi namgay257,

If your Mac froze during installation, you can restart the update via macOS Recovery. Unfortunately, you will have to download the update again (unless you made a bootable installer earlier).

Power on your Mac while holding down Command-R (assuming it's not Apple Silicon). Release the keys when the Apple logo appears with a progress bar.

When prompted, enter your admin password. Then, select Install/Reinstall macOS, and follow the onscreen instructions.

What has neither been asked nor offered is the sub-model of your Macbook Pro. No all Macs that can run Catalina 10.15 can run Big Sur.

Please do "About this Mac" to find your sub-model

and either tell us what you find, or look at this list of Macs that support Big Sur.

Ok. Looks like the macOS installer hasn't updated the local recovery volume then. In that case, I recommend booting the latest RecoveryOS over the Internet: Hold down Option-Command-R as you power on your (Intel) Mac. Release the keys when a spinning globe appears, or when you're prompted to connect to a Wi-Fi network.