What happens to Superman if he was around multiple yellow suns, does he powers multiply with the suns?

Good question. In none of the comics does Superman ever go to a planet with a double sun. I guess it would make some sense that two yellow suns would give him double powers. There is not an astronomical possibility of there being more than 2 suns in a solar system. And, usually, you have a yellow or red sun and a dwarf white sun; so I'm not sure the scenario you speak of would ever actually occur.