Hello,
As you know there are multiple buttons on the Single Product page. One is Add to Cart and the other is Buy Now. The Add to Cart button when you click adds Product to Cart and shows you the Cart display as it is selected under the Dashboard > Theme Settings > Shop > Shopping cart widget > Action after add to cart. So, if you have selected their Display Widget then it will show the Off Canvas Cart display. If you want you can change it too: https://snipboard.io/vdMiIs.jpg
The Buy Now button redirects to the Checkout page or Cart page as you have selected under the Dashboard > Theme Settings > Single Product > Buy Now: https://snipboard.io/Xle7nA.jpg
So, right now on your Site Add to Cart button is displaying a widget as you have selected under the Theme Settings. So, you change that accordingly as we have mentioned above.
Hope we have cleared out the doubts !
Best Regards.