New iOS 8/ 9 and iOS 10 for old iPhone, iPad model getting stuck app during download/ Update or install the app store. On my personal experience and my readers experience on the stuck app on iPhone/ iPad, I recommended the possible solved solution for your iPhone 7/ 7 Plus, iPhone 6S, iPhone 6S Plus, iPhone 6/ 6 Plus, iPhone 5S/5, iPhone 4S/4.
Possible fix and solved solution for Stuck app on iPhone, iPad or iPod Touch
Note: Low internet speed one of the most hesitating reasons behind stop app download from app store. So measure Mobile data/ WiFi internet speed on Speed test checker app. Available for all Apple devices and Platforms. (I am not talking about WiFi signal strength, Sometimes full signal strength lose data packet).
Not enough storage space, Means free space should be greater than your app size. Navigate to check current free space Settings > General > Storage & iCloud Usage > Under Storage section (Available storage is a free space for install app or save files)
Once Reboot your device by restart or force restart iPhone, iPad and iPod Touch. (Press and Hold sleep/ Wake button for restart or Press and hold Sleep/ Wake button + Home button at once)
Might be apple server connection fail, you need to be a re-login for creating a new login session. So, Sign out from your device completely, Settings > iTunes & App Stores > Tap on Apple ID > Sign Out
Done your job through iTunes installed on Mac/ PC. Connect your iOS device with PC via lightning cable and From iTunes > App Store > Remove stuck app or waiting for the app from there > install from there and sync with iPhone/iPad/ iPod from iTunes button.
Above solutions are the most helpful on the Stuck app on iPhone, iPad or iPod Touch running on iOS 11/ iOS 11.2.2 or Other.