Reload page, to see the product in the cart

I have the following problem:

When I build the article page and the add to cart button with gampage, I first have to refresh the page so that the article appears in the cart, how can I prevent this?

Also the side shopping cart is not inserted as soon as I add an article.

Does anyone have a tip? Is this an Ajax problem and if so, how can I fix it?

Link to example:
https://lets-bastel-shop.de/products/hirschkopf-bauanleitung?_ab=0&key=1730204693320

Can someone help me?