(iPad) App Photos dont stay saved/cached


i have got 2 iPads and an Apple TV on which i run Pydio.
The problem is that the pictures i upload to the server, dont get cached/saved, so that i have to load them everytime i open the app.
The other problem is that the documents dont get updated or sometimes not even loaded The iPads and the Apple TV dont really sync properly with the server.

Is there a possibility to regularly synchronize and save them locally on my devices?

Thanks in advance!