Running FreeBSD server behind a firewall with nat

[Roman Kouzmenko]

Hi,
 
I'm really new to FreeBSD and UNIX, and I have to configure it to host a
webserver. After a week I've managed to install Apache/mySQL/PhP and get
everything running as I want it on my local network.
 
Now I need to put it on the Internet, so that the developers can take
control over it (ssh, ftp). The problem is that at the moment when I
activate one-to-one nat on my hardware firewall for this machine, the
services stop working and behave strangely (for example, if I connect to
the box using ssh, it prompts for the login and nothing else happens,
ftp doesn't work either). If I try to reboot, sendmail doesn't start at
all (it just hangs, so I have to hit ^C to stop the script).
 
I haven't found any information about configuring this correctly on the
Internet, so I hope I can find an answer here.
 
Thanks!