I doubt that your hotspot/VPN provider supports manual port forwarding
In the moment when you are using a hotspot/VPN, your external IP is either a shared (hotspot) or a different one (VPN). In both cases I don't see any way to setup port forwarding. Of course I can be wrong and your hotspot/VPN provider has proprietary support for it
Yes, I meant api.jdownloader.org (sorry for the typo)