how to change the workspace background color without changing the fill color of the objects?
how can I change the workspace background (artboard) color without changing the fill color of the objects?
I'm new in this program and want to work with a grey color in the workspace (white as default) but when I change it, it change all the whites colors in the scene, it means that when I want something white I can't because it's grey now.
I suppose you mean you changed the setting that governs the paper colour? If you do that, all white objects will take on the background colour, because in Illustrator 'paper' means 'no ink'.
In order to work with a coloured background, don't change the paper colour. Just draw a large rectangle with a fill in your desired colour, send it to the very back of your layer stack and lock it.