Large apps or updates can sometimes take a long time to download or even stall if your connection is bad or there’s an issue with the App Store servers.
Alternatively, you might be downloading lots of apps at once and you want to pause the low priority apps until the important ones have finished installing.
Either way, you can pause app downloads until a more convenient time.
Tap the app icon on your Home screen. The progress bar will stop and Paused appears beneath. To continue the download, simply tap the icon again.