I have the version on nexuiz that is installed by ubuntu when you do:

sudo apt-get install nexuiz nexuiz-music

I have tried to update to the new 2.4 by doing a :

sudo apt-get update
and
sudo apt-get upgrade

but it does not work

what is the command to update to the latest version of nexuiz ? if there is any.
if not what is the best way to play the 2.4 version ?

2.4 is not in the repos yet. Basically (in ubuntu) nexuiz is synced with debian's repos. So you will not see 2.4 until it appears in the debian repo (which could take a few months unfortunately)

I am an asshat and my Nexuiz 2.4 will break

DON'T FOLLOW THIS ADVICE. Ubuntu could overwrite it that way at any time.

Just extract the zip and run Nexuiz from there. Much less hassle, and not going to break.

yeah, that is what i did. Just uninstalled the ubuntu version finally and play from the unzipped folder, did not know at first that nothing needed to be installed.. thank you all