I have many polygons that are adjacent to each other, and others overlap slightly. I need to merge them and sum up their attribute (Area per class). I attach an image of my problem (Screenshot of my merged polygons. Each color represents a landcover class)
I am able to merge the polygons using the function "merge Layers" from the MMQGIS plugin. But the adjancent polygons of the same type are not dissolved, nor their Area summed up.
I tried already using the function Dissolve (per Area) and doesn´t work either.
I am beginner in QGIS. I am working in QGIS 2.12.3 in a PC.