It can be very hard, especially when you have not registered the HomeServer in the Gira portal, which you probably didn’t because you have an educational version ;)
I have the idea that the Gira Portal Always gives some assistance when logging in remotely (from the internet).

What I did (and seems to help)
– Do not enable all the designs in the Quadclient, only the ones neccessary (so if you have an iPhone, disable the iPad, Android, 1366×766,..etc). Otherwise it takes much time to load and might give a timeout.
– Check with telnet (from the internet) is anything is listening on port 80.
– Do you forwarded port 80, 1-on-1 ? (So, port 80 to port 80) Or did you forward port 8080 to port 80 ? Do you have router logs?
– I’ve seen cases with mobile providers NAT’ing you 2 times which make it very hard to connect remotely, some providers (for mobile phones) offer you an APN with a public IPv4 address, that might help
– I have ‘direct line’ in the homeserver/experte project settings. Also make sure the gateway and DNS servers are setup correctly.
– Does it work from a PC qith the quadclient connected (from another subnet (routed) or over the internet?)