In object mode I try to add 3 mesh circles plus 1 Uvsphere but I can only select and work in one circle. The rest objects turn pink when I select them but I see no vertices. What I am doing wrong?
You’re not doing anything wrong, that’s how Blender is supposed to behave. When you add new objects in object mode, you get completely new, separate objects. If you want to edit three spheres as the same mesh, you add the new shapes in edit mode.
If you want to “repair the damage,” use join objects (Ctrl+j) when two of the objects are selected.