Add to Cart links with options and custom fields

For a shop that produces products on behalf of the customer, I am creating a page that displays the entered name in a preview and calculates sizes in PHP (as an overview for 20 or more produkts). For this page, I need an Add to Cart button that passes the entered name (Custom Text Field), the selected color (Custom Drop Down Field), and the selected height (an option in a dropdown) to the shopping cart.

All attempts to accomplish this via a link have failed thus far. This link adds the item to the shopping cart twice:
http://168.0.101:8060/index.php/index.php?option=com_hikashop&ctrl=product&task=updatecart&product_id=1&quantity=1&Itemid=153&hikashop_return_url=http://192.168.0.101:8060/index.php/&hikashop_product_option[4]=68

Once for the base item and once for the selected option. I am unable to get the custom fields into the shopping cart.

How should the link be structured?
Alternatively, a JavaScript Add to Cart would also work, but I am missing the parameters and my programming skills are reduced to vb.net