In order to get a cubemap to work, I need to copy the bsp file to portal2_dlc1/maps (if I don't, when building the cubemap an error message says "no sp_(my map's name).bsp found in portal2_dlc1/maps" and the game crashes), enter the game, buildcubemaps, and delete the bsp from both portal 2/maps and sdkcontent/maps otherwise the reflections won't show up. I need to do this again for every new version I make of the map.

and it's not all: when someone else download the bsp file, the reflections doesn't work for him, even when he puts it in portal2_dlc1.

^[solved], the player need to replace the materials folder from portal2_dlc1 with yours (however, if anyone knows a way on which i don't need to repeat the whole process with every new version, please tell me).

any suggestion? (please and thanks)

Use the search function, there are many threads about this.

Normally you put your Map to Dlc1 maps folder (remove it from the Portal 2 map folder), build cubemaps and have fun.
You dont have to remove it from the SDK files.
Other people will normally just get reflection errors if you rename the map after you built cubemaps.

I know, @spongylover I found nothing about my exact problem, @skotty I need to go through this headache every time I compile the map...
(about the sdk files, if i don't delete them it would load them onstead of the one in potal2_dlc1. Also, overwriting the ones in portal 2 and sdk with the one from portal2_dlc1 didn't work, even if I overwrite the materials folder as well)