Opin Poll: Buttons look a bit off/ description are in a difficult contrast

[fredewe]

URL: https://opin.me/en/projects/presenting-the-nwe-poll-modul/
user: user
expected behaviour: Buttons and descriptions are visible
behaviour: Buttons or descriptions "previous" and "next" look of or are in a difficult contrast
important screensize:
device & browser: MacOS, Safari, Chrome, Firefox
Comment/Question:

Screenshot?
Safari:

Chrome and Firefox: