Can't download any app from AppStore!
First I'd suggest you to try perhaps thru an alternate internet connection.
If that doesn't resolve the issue I'd suggest you the following since you're stating that this happens every time you try to download an app or an update then I assume that this happens by every app and resetting your iPhone doesn't either work then I'd suggest you to try signing out of the App Store then restart your iPhone and sign into the App Store and try again to download.


See my answer in this post