If you can’t download or update apps, or if apps get stuck
If apps don't load or update on your iPhone, iPad, or iPod touch, learn what to do.
If you can’t download or update any apps, including free apps, and you see a message about billing or payment, learn what to do.
Some apps might get interrupted while they're downloading. Try these steps:
Connect to Wi-Fi
If you’re using cellular data or Wi-Fi and have issues with an app, try to connect to another Wi-Fi network. You can use cellular data for apps up to 150 MB* in size.
To check your Wi-Fi connection, try streaming a video from the Internet to see if it loads quickly. Get help connecting to Wi-Fi or contact your Internet provider for more help.
If you can't download or update apps, or if apps get stuck - Apple Support
https://support.apple.com/en-us/HT207165