Any Users Here Can Help With Fillazilla Server Issue

Hi,
I am using the FileZilla Server & sometimes it runs into an issue where i am told i am behind a NAT Router.
I have made a thread on there site but just pointed to a url.

Having learning difficulties i am not sure how to tackle it.
I am able to follow advice from members but reading from a sheet i find hard.

Most days my set up works fine but i need to set up the network config to overcome this issue.

Can anybody assist.
Many thanks.

https://forum.filezilla-project.org/viewtopic.php?f=6&t=48860&e=1&view=unread#unread

https://wiki.filezilla-project.org/Network_Configuration