Html Css Online

Don't understand how to use this, sorry?

On this site https://www.geodanmark.dk/anvend-geodata/kurser-og-workshops/tidligere-afholdte-kurser/webinarer-om-kommunale-friluftsdata/ if you scroll down would like to change the code examining dark green background og black text which is NOT easy to read.
And so I will tell the people behind this code that a link to the last video is missing. :-(

<h2 class="vc_custom_heading" style="font-size:20px ;color:#2d3e50 ">Optagelser fra webinarerne</h2><div class="geo-box-content wpb_text_column" style="color:#2d3e50 "><p>Webinarerne blev optaget, og du kan se optagelserne her.</p>
</div>

<div class="gd_custom_button"><a href="https://vimeo.com/531246151/ac5e03582b" style="background: #4c5f35; border-color:#4c5f35;color:#ffffff;">Introduktion til friluftsdata (19. marts 2021) </a></div>

<div class="gd_custom_button"><a href="https://vimeo.com/534460799/6ce70f4c1a" style="background: #4c5f35; border-color:#4c5f35;color:;">Skab og upload data (8. april 2021) </a></div>

<div class="gd_custom_button"><a href="https://vimeo.com/536833925/2a17ee3865" style="background: #4c5f35; border-color:#4c5f35;color:;">Ajourfør data (14. april 2021) </a></div>

<div class="gd_custom_button"><a href="https://vimeo.com/540543708/adfcba1730" style="background: #4c5f35; border-color:#4c5f35;color:;">Udtræk og hent data (22. april 2021) </a></div>

<div class="gd_custom_button"><a href="https://vimeo.com/542143628/6a4f5189cc" style="background: #4c5f35; border-color:#4c5f35;color:;">Upload og tilknyt billeder (27. april 2021) </a></div>

<div class="gd_custom_button"><a href="" style="background: #4c5f35; border-color:#4c5f35;color:;">Status, opfølgning og afslutning (3. maj 2021) </a>