Is this possible with q3map2 ?
If yes - how ?
Thank you !
Yes, i know this but its a bsp file.
Trying this
q3map2.exe -convert -format map d:\q1maps\dm1.bsp
returned the error
d:\q1maps\dm1.bsp is not a IBSP file

There’s no way to convert a .BSP file to a .MAP file automagically with any degree of success.
At best, you might be able to find a utility to make a very crappy conversion, that you can load into GtkRadiant and manually rebuild the entire level from scratch again after loading the chopped-up, useless brushwork whatever .bsp->.map converter gives you.
Download this, works great for me;
http://www.ydkgaming.com/files/tfc/winbspc12.zip