Very serious topic, indeed...
First of all, in the language I speak, we make a distinction between "cook" and "bake". I would not cook the pizza but bake it (in a stone oven, around approximately 350 degrees Celsius). Now, we skip the whole recepy and go directly to the cutting of the pizza.
Use a knife for the cutting itself. Eventually make it wet with a humid cloth between every cutting, that prevents that pieces stick to the blade of the knife. And then, dear Bob, now we're right into the culminating point of your problem, use a "spatula" (or two, depending on the width of every piece) and glide it gently under the slide, then lift it upwards (not pull it), I insist, lift it up so that everything (olives, tuna, whatever topping you use) stays in a horizontal position, and then stay focused and concentrated, direct the slice while keeping everything in a horizontal position till you are above the plate you want to eat off, and now, slowly again, and horizontally, let it all down. Slide the spatula nice and gentle from under the slice.
If this is too difficult or if you don't succeed, maybe you drank too much wine while the pizza was baking, I don't know.
Good luck.