Dialplan PAP2 for Forwarding calls from VOIP modem to Freepbx/Asterisk


I’m completely new to FreePBX/Asterisk. I would like to get see if my current project is possible at all, so hoping I can get some feedback here.

My current ISP has provided me with a voip modem, which I don’t know the voip settings for, and I’m pushed to using it.
I would like to connect that voip modem to my PAP2 on line 2, and then use my own PBX Solution (FreePBX/Asteriskt). On line 1 I have attached a standard analog phone RJ11. My first step would be to forward all calls from line2 (incoming) to line1 (where I have the phone), and using FreePBX/ASterisk as proxy.

Is this possible?

I can see my pap2 sending out registration events to Asterisk/FreePBX (Using FreePBX v13).
How ever when calling my voip router from and external number and having it connected to the PAP2 i get the busy tone and no events in the logs. My guess is that the dialplan needs to be changed and point out my FreePBX server?
I have created two extensions in FreePBX for each line

I do realize these questions are very basic/noobish, so would be very happy if someone point out some good documentation or examples where I can start.

Best Regards, S