Q: why take so long time to update?

Welcome to Apple Support Communities

The update is frozen. Press Alt, Command and Esc keys, choose App Store and close this application. Then, restart the computer and install that update

Check your download speed >  Speedtest.net - The Global Broadband Speed Test

Less than 10Mbps, contact your ISP for upgrade options to broadband.

We have no idea of your connection speed or what you're trying to update, so no possible suggestions would be worthwhile.

And that's why I posted the link for the speed test. So that is, "worthwhile" ...............

FYI:  Trying to discredit other contributors advice in ASC is frowned upon 

Didn't see your link until I posted. When I posted, there were no other responses until after I posted.

FYI:  Trying to discredit other contributors advice in ASC is frowned upon 

Look at the time postings, my post was 2 minutes before yours.

so no possible suggestions would be worthwhile.

Regardless, that statement is confusing.

Until the OP clarifies his situation, we can only blindly guess about possible solutions.

What software were you trying to update? Was it from the App Store or another source? How many times have you attempted a download?

And, as Carolyn previoulsy suggested, it would help to check your Internet speed, because there could be an issue with your service.