Hi Benni,
The icons come from FontAwesome, so in order to make them work, you have to visit this home page first:
https://fontawesome.com/v4.7.0/icon/facebook-square/
After that, you just have to click on the icon you want and get the code. For example, if you wanted the Facebook Icon you’d have to use:
fa-facebook-square
Regarding the about section, it’s now fixed on version 5.0.3 😉
If you have any questions, let me know
See you