If you have recently restored your device or if you updated a large number of apps at the same time, then you may experience issues with deleting or opening the app on your iOS device. This can cause apps to become stuck in a 'waiting' state.
Here is a quick fix on releasing the game from your device:
Complete iTunes Sync: The apps that you've installed on your iOS device must also be on iTunes if you've synced before. In this case, what you can try to do is remove the app in iTunes, re-sync with your device so that the app gets removed there as well, and then reinstall the app from the App Store.
Connect your device to your computer and open iTunes.
"Remove" apps that are stuck in 'waiting' or not able to be deleted from the device via iTunes. To do this, just click on your device from the sidebar, click on the Apps tab and from the list, select the app that's causing the issue, click 'Installed' – this will change to 'Will Remove'.
Sync your device via iTunes. The app should now be removed from your device.
Once you've removed apps this way, you can re-install them if desired. For the apps that are stuck on 'waiting', you can just remove them this way and then re-install them on your device through the App Store (not through iTunes).
Do a fresh Restore from Backup: A fresh restore from a backup you did recently is a good way to restore things back to normal. If you have a backup on iTunes, you can use this backup to solve the issue.
You can restore from an earlier backup by clicking on the Restore option in iTunes. This will prompt you to choose a backup (if there is one).
If there is no backup, the restore will upgrade your iPhone to the latest iOS version along with removing all the apps. If you are not particular about data at this point, you might do a fresh restore too. It's like starting from scratch, but you can get all the apps back via the App Store → Purchased section.
Reset Everything: Not known to work all the time, but resetting everything might just help you fix the issue of apps stuck on waiting.
To reset all, go to Settings → General → Reset → Reset All Settings. This won’t erase any data.
Check Download Queue: A long download queue can also cause apps to become stuck on waiting or loading. You can fix this easily.
Open the App Store
Click on Updates
Click on Purchased
If there are numerous apps stuck on "Installing", you should remove these apps via iTunes and then re-sync.