Getting (ERR= -3259) error while software update on iPhone

See this --> If you see an error when you update or restore your iPhone, iPad or iPod - Apple Support (IN)

Or this --> iOS update and restore errors - Apple Support

Error 53 --> If you see error 53 when you update or restore your iPhone or ...

Error 9, 4005, 4013, 4014 --> If you see error 9, 4005, 4013, or 4014 when you restore your ...

Try updating iOS after each step.

• Try to Forget the WiFi network and add it again
• Try another WiFi network 
• Toggle sets automatically off and then on
• Reset your network settings
• Force restart your device
• Remove any beta profiles, if applicable

• If everything fails: - Use iTunes or Finder (for macOS Catalina+) to update your device instead of over-the-air
• Get help with iOS updates and restore errors - Apple Support
• If you see an error when you update or restore your iPhone, iPad

VPN or proxy connections might prevent your device from contacting the update servers.

• Get help with over-the-air iOS updates - Apple Support
• Remove and download the iOS update again

Here are some things you can try:

Basic checks:

• Make sure your iPhone is connected to a stable Wi-Fi network. A weak or intermittent connection can cause update issues.
• Ensure your iPhone has enough storage space. The update might not be able to download if your storage is full. Go to Settings > General > [Device name] Storage and see how much space you have available. If you need to free up space, delete unnecessary apps or files.
• Force restart your iPhone. This can clear any temporary glitches that might be causing the problem. For an iPhone 7, press and hold the Sleep/Wake button and the Volume Down button simultaneously until you see the Apple logo.
• Sometimes, a simple restart can resolve temporary software glitches. Turn off your iPhone, wait for a few seconds, and then turn it back on.

1. 1. Restart the device. That's it.
   2. Still not solved --> Force restart iPhone - Apple Support

More advanced troubleshooting:

• Update your iPhone using a computer. Connect your iPhone to your computer with a reliable cable and open iTunes (or Finder on macOS Catalina or later). Select your iPhone in iTunes/Finder, click "Check for Update", and then download and install the update. Update your iPhone, iPad, or iPod touch - Apple Support (IN)
• Restore your iPhone. This should be a last resort as it will erase all of your data and settings. Make sure you have a recent backup before you proceed. Return iPhone settings to their defaults - Apple Support (IN)