Hello @eutaw,
I have checked the page in question but didn’t see the textarea field:

Did you hide it? In case you will add it again, the issue is because of the following custom CSS:
.wpcf7 input[type=\"text\"], .wpcf7 input[type=\"email\"], .wpcf7 textarea {
background-color: #fff;
color: #000;
width: 680px;
}
Please update that CSS to this:
.wpcf7 textarea {
background-color: #fff;
color: #000;
}
Remove the width property. That cause the overflow. This line .wpcf7 input[type=\"text\"], .wpcf7 input[type=\"email\"],
is incorrect too. No need for the backslash. This is correct : .wpcf7 input[type="text"], .wpcf7 input[type="email"],
if you want to include textfield selector.
Hope this helps.