Can't add products to my cart :(

[Flatiner]

When I want to add a product to my cart nothing happens. I'm redirected to the shopping cart but no items in it..
I'm not a developer and the former one has stopped working.. so I'm on my own.

Can someone help me? I read different posts but I don't know where to start.

My site: www.reanimatie-oosterwolde.nl

Thanks in advance!

[Studio 42]

You have 2 problem(at least)
fancybox is not loaded > certainly a setting in the Virtuemart config.
You load a old squeezbox script using mootools(obselete because Jquery is now used in all case in Joomla 3.8+)

[Flatiner]

Thanks for the fast reply!
Do you have a solution how I can solve this?
I'm a complete noob with those kind of stuff..