hi, i’m trying to export my mesh as a single subtool and if i do on the negative subtool: polygroup-group as dynamesh sub-mergedown the negative subtool become positive and doesn’t remove anymore mass… i tried also to use merge boolean but the mesh deformed 
Assuming you are trying to fuse the meshes as opposed to simply grouping them together in the same subtool, I would recommend using the Live Boolean feature in this case. It will allow you to preview exactly what the resulting mesh will look like even with a mix of different boolean modes, rather than going through complicated merging procedures.
After you get it set up the way you’d like, use Tool > Subtool > “Make Boolean Mesh” to create an entirely new (not a subtool) fused tool in the tool list.
i tried but doesn’t work, the mesh deformed like in the image
Try giving the different pieces some thickness, especially if you’re using dynamesh for the booleans (dynamesh prefers water-tight volumes)