Even though Firefox is very pratical there was a very annoying effect: when scrolling the display often stutters heavily and gives you the impression that Firefox is much slower than other browsers. But there is a possible solution as well. After I activated the setting for
layout.frame_rate.precise in the advanced configuration (about:config) the stuttering disappeared.
You have to restart Firefox before the change becomes active (for example by removing it in the list of recently used apps).