Raspberry pi3, Domoticz, Imperihome, how to connect to an external network?

Hello.
I am building a substitute for a smart home, the construction is based on Raspberry 3, Domoticz and control from an Android phone via Imperihome.
Everything (relay control, temperature measurement etc.) works fine but only in the local network.
How can I make my Raspberry visible from the Internet (other network)? I read a bit about the "no-ip" website, but I don't know what to upload, what to set.
Some data:
Netia supplier
Router Spot
Raspberry 3 - Raspbian Jessie With Pixel.

On the router, you need to forward the external 8080 port to the internal network Raspberry IP address.
If you do not have a fixed IP then you must use the DDNS service (no-ip, freedns, d-dns) to update the current IP address.

Exactly as Zdzicho wrote, I used the no ip service, redirected ports and it works
Thank you