For styling I used:
The project "broke" all of a sudden. $npm start no longer worked. Even pulling earlier version from GitHub on a different computer did not solve the issue. What solved the issue was:
$ npm update --legacy-peer-deps
The Solution was provided here: facebook/create-react-app#2436
It is possible that on MAC the fonts will look different with spacing looking "off". I used Arial for my font.
I was not able to modify the position of an input placeholder for Firefox. Chrome and Edge worked fine, but not Firefox. I selected it with -moz... and could change it's color, so the css selector worked, but margin, padding, transform didn't not move the placeholder text.