Modal Pop Up does not scroll

Modal Pop Up does not scroll

Hello, I need help with a problem. I am using the modal pop up and linking to a page via shortcode. It works so far that you can click the button and the linked page pops up. Unfortunately, however, there is no scroll option. Especially with smartphones, I have the problem that the page is cut off. This is particularly difficult with the contact form, as the send button is cut off. How can this be solved?

Many thanks in advance and best regards, Axel

The page I need help with: [log in to see the link]