You need to add a section to the site and function promo code in the shopping cart.

Hi all, I have 3 problems: 1 – the site already has detailed sections. There are tables, chairs and so on. You must create a new "decor". That is, it should be reflected in the menu and it should be possible from the admin panel to complement it, like the others. It is absolutely identical in design. 2 – In the cart you need to add a field code that activates the discount 5 to 10 per cent. 3 – There is a small but serious problem, when scrolling through the pages, you receive the error You have some incorrect JavaScript code (AJAX Products Filter). You need to fix it.