The update is writing for me update requested for a half hour

The regional Apple Update servers are likely to be very heavily loaded at this time - and not have sufficient capacity to immediately serve all update requests.

Whilst your update should automatically commence when capacity is available, you might be best advised to wait and try a little later.

A further possibility is that your Broadband Router may be unexpectedly blocking access to some internet resources. In such instances a restart of the Router can resolve the problem. To restart you home router, disconnect power - then wait at least 30 seconds before restarting. When you router has rebooted (which may take several minutes), force-restart your iPad:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On an iPad with Face ID: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

You must have a stable Wi-Fi connection.

Or connect to a PC with the latest version of iTunes installed.