Hox can i fix this?

When I select many objects and try to apply a trasform operation (rotation, scale, etc.) on the right panel it only affects one object, and sometimes one object that is not even on the ones selected (but somehow has the yellow dot), but if i use the command R, S, etc. it affects every object selected, how could i fix this?

As in the picture, i selected those 9 pieces above to rotate on the panel, I started rotating (transform-rotation- x axis) but the one rotating is de big piece below, why?

Properties Editor only displays properties for the active object (last one to have been selected or deselected by a single click).
To change rotation on 1 axis for several objects of a selection, you need to press Alt key while changing the value.
Or you can change it for active object and then, do a right click on value to call a menu, choose Copy Single to Selected.