Why I can’t download apps on my phone

You need about 6 GB device storage and good Service & Wi-Fi.

See the following Apple articles:

Update your iPhone, iPad, or iPod touch

Update your iPhone, iPad, or iPod touch - Apple Support (IN)

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

If your iPhone, iPad, or iPod touch won't update - Apple Support

You can do the update via PC, see this Apple article: Update software on iPhone, iPad or iPod touch in iTunes on PC

Update software on iPhone, iPad or iPod touch in iTunes on PC – Apple Support (UK)

If you have a Mac see this Apple article: Update your iPhone, iPad, or iPod touch with the Finder

Update your iPhone, iPad, or iPod touch with the Finder - Apple Support

Can’t download -

Try a different wifi network; office, library, coffeeshop.

M1 Mac mini, macOS 13.1; Watch, series 7 GPS/cellular, watchOS 9.2; iPad Pro 2nd Gen, iPadOS 16.2; iPhone 12 Pro, iOS 16.2; TV 4th Gen, tvOS 16.2; HomePods, audioOS 16.2 and Airport Express w/ Airplay 2