Ok, I will try. Although I dont understand why are you saying that C3200 doesnt support vpn server... as I have the option to select it from Internet Connection Type.

So, again my goal is tu access the HDD from outside. Here is what I did so far: 

Conected the C3200 to the internet router/modem that was provided by the ISP (which is in bridge mode so it wont get in my way) . It was connected by Dynamic IP . Added the USB HDD and set up the sharing settings... checked the box for the internet ftp access. At this point I tried to connect to the ftp address (that my router showed) from my phone (which was not connected to the local network) and everything worked as it should. I could see all the files from outside my local network.

Then I moved to the next step. As I have a paid VPN service, I wanted to add the VPN to the router so my entire local network will benefit from the VPN service, including my 2 TVs. In connection type where it says Dynamic IP, I selected L2TP, added my User/Password, left Dynamic IP checked, added the VPN server address, and then reconected to the Internet. At this point the ftp from the USB sharing settings has changed to probably the new VPN IP address. The VPN is working fine.. and evey device in my home is now listed on the country server I choose. The new ftp starts with 10.0.1.... so when I tryed this the phone will always give connection refused very fast. 

For some reason the router refuses this connection, and there is my question. Is there anything I can do ? or should I just forget it.

P.S. If i try to connect to this VPN ftp from within the local network, it works.

And sorry for any mistake in expressing myself... as english is not my native language, nor am I an expert in networking etc... :)

I understand.. and thanks for the reply, as I said I`m a beginner here. If by my WAN IP you mean my ISP IP, then it has not change... Anyway I gave this up and will just try and use it without the VPN service. 

But now there is a new problem. Since my USB DRIVE (WD MY BOOK) has sleep timer, after it wakes up the router will change its name from sda1 to sdb1.. or vice versa. That will make it unavailable to any app, from the network,  that already used its old name 

Is there any way around this ? 

I thought I found a solution for the name change... I've added a USB stick that wouldn't go to sleep in an attempt to keep the names sda1 for the stick and sdb1 for the HDD drive. 

It worked for a few days... Then the drive changed to sdc1... So everything in the house related to that media folder stopped working. Anyone think of a solution? ... Or it would be easier to just sell this router and move on.