Can you figure out centre of a complete eclipse balloon? Big bang is that tiny fraction of second between zero air in Balloon to perfect eclipse balloon. And it's not done yet. It's still blowing outwards dominated by dark energy. Think of galaxies as polka dots on balloon when their is no air. Now with a air filled balloon those dots are light years apart. It's not a 100% accurate picture as it's missing gravity and why some galaxies are bound to be merged whereas others drift apart. But it's a good imagination to clear your head that there is no center. Air is filled in the balloon everywhere at same time.