I did encounter a new Apple user that had a similar or same issue. We found the app later by cheating. We emailed him a pages document and it opened.
I boiught my iMac with preinstalled Apps - Pages, Numbers etc. But they are not to be found on the machine.
The best answer seemed to be to go to iTunes store and download them - rather a pain - it is said to be taking 4 hours to download Pages alone.
Am I missing something ?
Hoarding photos on your phone?
Those picture are hogging memory and could be slowing down your phone.