I have wait 4 months and now my substrate is black color! But the problem is that the soil itself has no smell. Like I can smell nothing when I stuck my nose inside. Is this good?
Color of substrate is only decided by what ingredients you added in there and the temperature of fermentation. In usual cases (when you only added what's known in Internet), higher the temperature has reached, darker the substrate color is... You may not be able to smell it. Smell doesn't really matter as long as it is not terribly bad...