Network issues

Optimize the range of the mobile network, see this Apple article:

If you see No Service or Searching on your iPhone or iPad

https://support.apple.com/en-us/HT201415

For a good Wi-Fi network, see the following Apple articles:

If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network

https://support.apple.com/en-us/HT204051

Connect to Wi-Fi on your iPhone, iPad, or iPod touch

https://support.apple.com/en-in/HT204204

Check your mobiel data plan if you want to update using mobiel data, contact your carrier.

See the following Apple articles:

Update your iPhone, iPad, or iPod touch

https://support.apple.com/en-in/HT204204

If your iPhone, iPad or iPod touch won’t update

https://support.apple.com/en-us/HT201435