Hi,
I browsed and clicked on the picture and it was displayed in full screen. This may be related to your Impulse Theme. You can ask Impulse Theme customer service.
Or you can go to the “Customize” setting of the Shopify theme to find out whether you can choose to enlarge the picture in medium.
But I think enlarging is also good. I can see the details of your pictures clearly. Enlarging has its own advantages.