It is conceivable that the initial update file you download is corrupted and will not install. You must delete the corrupted update file in this scenario. Download the update file again after the broken file has been totally deleted. Here's how it works:

1. Go to your iPhone's Settings.
2. Select General.
3. Select iPhone Storage.
4. In the list of apps, look for the iOS update file.
5. Select the iOS update.
6. Select Delete Update.
7. After deleting the file, navigate to the Settings->General-> Software Update menu.
8. Then, get the most recent iOS update.
9. check if this method work or not