1) Simple products have the option “Ajax add to cart” that you can ON/OFF in Theme Options > Single product. Variable products do not have such option, that’s why the page is reloaded after adding to cart and displays info message. If you disable “Ajax add to cart” option for the simple products you will get the same message after adding to cart.
2) It’s because of the lazy loading for the Products element. Try to increase the server max execution time to 60, probably the exiting limit is not enough to get and display the element content.
Or edit page, edit the 8theme – Products element and disable Lazy Loading for the element.
Thank you for you kind answers and support, they all worked and we almost have the e-store 100%! We still have 2 more questions: why haven’t we got any product in the “New Products” tab in the homepage (we’ve added 1036 products by hand and is none showing!!!!!)? Also, is there any way to set that product tab manually? Secondly: can we also set manually the “Best Sellers” product tab?
Edit your page > edit the Product element that you have in the New products tab and check the element settings. You should have products type > all, sort by date and choose the ask/desc order. To show bestsellers edit the next tab content and product elements and choose the bestselling in the product type http://prntscr.com/ph1qjs