Thanks for the hint , it works to use just a button and add a link like this:
https://api.whatsapp.com/send?phone=&text=Lass%20uns%20zusammen%20brunchen!+https://www.ayurvedaroom.ch/brunch
Which leads to the WhatsApp Message:
Lass uns zusammen brunchen!
https://www.ayurvedaroom.ch/brunch
The same I did on https://www.ayurvedaroom.ch/kochkurse
CHECK IT OUT ON MY SITE 