OpenVPN client on Turris OMNIA and port forwarding problem

I’m really still a noob on this area but after a lot of googling I started to install OpenVPN client on Turris OMNIA.
It seems to function okay for the devices at home going outward on the internet.
But when I’m outside (mobile internet)

  1. I can reach my NAS (calendar, fotos, music etc)
  2. I cannot reach my devices which need port forwarding (like security cameras).

Any idea what can be the problem?