Help with decimation

I want to decimate a model that has aroun 11 million polys into around 4 million for baking in marvelous, but when I decimate, it only decimates the face and leaves the body as is. Is there a way for me to focus the decimation in the torso so that i can keep my face skin details?

I tried using masks but the limit of polys it lets me dacimate to is 1 million