I have a shapefile containing 6 classes of polygons on QGis 3.14. Some of these polygons overlap each others, but they're not geometry errors or duplicates, just polygons with different attributes. However I need to have maximum one entity at any place. So, I'd like to obtain, for each overlapping area, a new entity containing the attributes of the polygons that overlap. I can't make an intersection on a single layer, and the union tool gives me two polygons with equal geometries.
What should I do ?