I cannot move my x-axis to the Y = 0 - help

[Matthias]

this just cuts off the negative values, I think francesco wants to keep it.
Actually it's not so easy, here is a similar, older question:

Moving X axis up/down

ok, it seems what you want is for the xaxis ticks labels and alls going through the midline of the plot. ggplot doesnt give elegant ways to do this at present. There are a bunch of proposals at : https://stackoverflow.com/questions/17753101/center-x-and-y-axis-with-ggplot2 I would probably try https://stackoverflow.com/a/49202967/11726436