Hello,
1. When I try to add the product into the cart I get to this product page. Do you mean the megamenu? It is not a place for the products display. You can show products however it is not possible to add the product into the cart and keep the menu open.
2. Please make the full backup of your site and update the theme to the recent version. I will check this again if the problem persists.
3. As soon as you update the theme try to set pagination instead of the “Load more button” and check the issue.
If you have any questions please feel free to contact us.https://trekano.com/
Best Regards