I've moved your post to it's own thread where it will receive more attention. The place where you had posted it before, was not related to your problem.
There's no way to download an app that's not compatible with your device. I suppose it's an app that needs 64-bit, and your iPhone is 32-bit?
All newer apps in the App Store are 64 bit only and the remaining 32 bit apps will be removed from the App Store later this year unless they're updated to 64 bit compatibility before then.