Add extra input row CF7

Before I start with my question, I want to apologize for my bad English.

Currently I’m building a website for a sandwich shop in Holland. A lot of customers are now ordering via e-mail. I want to create the opportunity for them to order via an order form on the website.

Because the size of the orders are very different (sometimes 3 sandwiches and other times 13 sandwiches), I would love to have a ‘Add extra row’ possibility for the customers.

I’ve searched the internet for Order Forms plugins, but I can’t find a plugin that gives me this possibility. I think the easiest way to archive this, is to add a function to the Contact Form 7 plugin. After hours of searching I can’t find a solution to this question on the internet.

I hope there is someone who knows a solution to my problem. I’ve added a picture to make my question visual. The link of the website is http://v2.royals-amersfoort.nl , but the Order page (“Bestelformulier”) is not active because I can’t start without a solution to my problem.

Thank you in advance!

Best regards, Tom van der Weide