Remove render blocking resources

Hi,
I have a problem with a site, nail-couture.be , there are problems with the booking form, this seems to be caused by the following:
Remove render blocking resources.
Resources: Your page has 19 blocking script resources and 20 blocking CSS resources. This causes a delay in rendering your page.
Cloudfront, is this from WPMUDEV?
Can you tell me how to fix this please?

Thank you,
Rene