Hi Mikeyy, sorry for the delay. Before your answer I did figure out a restart myself. And that got things going. But my forum message was still not approved, so I couldn't alter it.
So in the end I managed to download stuff via DS Get via VPN. But all of my webservices were not reachable anymore. I read about that before hand, but thought a bit too optimisticly. After reading up on it, I got scared whether I would be able to have a VPN and run my webservices at the same time.
I would need passthrough of:
-webinterface of synology
To be honest I am afraid that I am not capable enough to make all those things work.
Take a look at 3rd point in my tutorial.
After you do that, you need to forward ports on your router, but if that worked before, I guess you already forwarded your ports.
Then you only need to connect to your REAL IP (IP given by your ISP), not AirVPN IP address and it will work.