Hi annapurna176,
It seems you're having some trouble downloading the update for your Apple Watch and we can help.
How are you trying to update?
If you're updating on your Apple Watch, try updating using the Watch app on your iPhone instead.
You could set them near each other and near your Wi-Fi router and connect them to the charger. This will make sure they have a good a connection as possible to each other and to Wi-Fi.
Here's info on how to update your Apple Watch:
Update your Apple Watch
Let us know if you've gotten this updated and we'll be here to help.
Thanks for using the Apple Support Communities.