Set all touchpad buttons to "Left Mousebutton"

I need help:
I want to use my touchpad like Ubuntu (Gnome3) or macOS: Clicking anywhere is “LMB”, two fingers touch and click is “RMB” (but its not so important). How can I do this in my X390 with XFCE?
And maybe I can disable Middle Mouse Button Paste as well. :wink:
There is no option for this like in KDE or Gnome3 in the settings menue.