Thanks for your answer! I am just new to After Effects so I don't really know how to apply the things in this article :/
I created my 2 evolution keyframes with the stop watch in the beginning and end and now I have to add some kind of expression I guess? But what does the expression has to look like that the evolution speed reacts to the audio?
I thought it would be so simple^^
If you are new to After Effects, this isn't the sort of project to jump into. You need a good, solid, trustworthy, basic tutorial series (that is, not some random YouTuber) to get you a foundation first. After Effects is much more complicated than it looks.
If you really must do this now, you'll want to learn how to work with expressions. The best place for that is MotionScript.com