After a long research, I found out that it should be possible to access my files over a vpn network.
Here is my setup : Routing and NAS Server is a Time-Capsule with 3 external drives.
VPN Router (OpenVPN) is a Raspberry Pi with Raspbian installed. Accessing files over the VPN from my MacBook is no problem at all.
Same for local services. Everything works great. I installed the OpenVPN App on my iPhone and iPad to get a connection to my VPN Router.
Works fine aswell. So the only problem seems to be how to access my stuff from inside the Infuse App.
I tried to add the share in the infuse app via the host name and (because often the hostname is not transmitted via VPN) of course the local IP of my Time-Capsule.
As I said earlier trying that stuff over the MacBook works flawlessly.
The IP from the outside network is different. (Time-Capsule 192.168.1.x) (Outside 192.168.178.x) (VPN Routing 10.8.0.x)
Any suggestions ?