If God exist as a finite person occupying a particular space, then how can he also be infinite, or everywhere at the same time?
He's not a finite person, existence is due to his presence, so how can he be finite? Being unlimited krishna maintains everything by his parcel expansion ( paramatma ) in which he enters into everything and maintains it. No one is equal to him, nor greater than him. Being omnipotent is what makes him omniscient, we can only be at one place at one time, Krishna by his omnipotence can be at all places at all times.