How to style "success message" (remove green box)?

Hi Guys,

Everything works great but the green box appearing after successful form submission does not match my webiste at all. Is it possible to edit it and how?

Also, apart from the message in the box, I get another message underneath “the link to the file(s) has been e-mailed to you”. I do not need it, especially that my website is in a different language. How do I remove it?

Thanks for your help.

https://www.ads-software.com/plugins/email-before-download/