Hi Anton;

Understandably, you have a lot of questions on starting with NetBSD.
I doubt if many on the list will have time to walk you through
everything, which is why there is lots of nice documentation. See below
for links to docs for your questions:

> ?Have the NetBSD computer connect directly to the internet, not through 
> any other computer

http://www.netbsd.org/Documentation/network/

and, since it seems like you have DHCP:

http://www.netbsd.org/Documentation/network/dhcp.html

> ?Run a softrouter on the NetBSD computer so my imac and an other 
> portable pc can connect through it to the internet

http://www.netbsd.org/Documentation/network/#simplenat

> ?Run an HTTP, 

You'll need to install apache (the most common web server) from the
ports:

http://www.netbsd.org/Documentation/software/

and 

ftp://ftp.netbsd.org/pub/NetBSD/packages/pkgsrc/www/apache-current/README.html

> MAIL

Depending on what you want to do, you need to follow one of the many
applicable how-tos on the web, ie:

http://plug.phoenix.az.us/step-by-step/qmail/

> and FTP server on the computer

http://www.netbsd.org/Documentation/network/inetd/ 

> ?Enable Telnet (or SSH, if someone please would let me know what that is)

http://www.tac.nyc.ny.us/kim/ssh/

> ?Make another account on the NetBSD computer so I dont have to use the 
> root account, and i want to learn how to use su(1)

http://www.netbsd.org/Documentation/misc/#adding-a-user
and 
http://www.netbsd.org/Documentation/misc/#problems-with-root

These are just from the mail netbsd pages and linked from other pages
that I look at. You will undoubtedly find much more on the web.

Hopefully this helps. Please take a look at these docs; they are meant
to help with exactly the types of questions you have.

Brad