it write me : "couldn't load maps/dm_slimepit.mapcfg" ??

Which version are you using & how did you install it?
There's indeed no dm_slimepit.mapcfg in Nexuiz 2.3, since the map has been replaced by reslimed. You might have some leftovers of an older version that cause the problem...

My version is nexuiz 2.3
I haven't got older version, it's the first time that I play nexuiz.
I have just install a frenchpack

piero wrote:I have just install a frenchpack

Well, that explains it. The french pack was never updated for 2.3 afaik, so either delete it or open the pk3 with a zip program and delete maps/campaign.txt (that should fix the campaign bug, but there might be more).

Thanks for your help, I will try it

It fixes the bug, I can continu the campaign, thanks for your help.
Do you know if a french pack for Nexuiz 2.3 will be created?