How to insert sections and hyperlinks in google maps infobox

I need to insert a google map on my website, however I want to insert sections and hyperlinks to documents in the infobox, which i can't seem to do in google mymaps.

Using this website as reference: https://www.odense.dk/dagtilbud/dagplejen/dagpleje-syd?areaid=50&areaname=Syd

It has a map with a section. Within this there are markers. In the infobox of the markers there are hyperlinks to a document.

How and where do i get started with creating something similar?

Any help much appreciated.