I switched to staging and now touchscreen works.
Content of /usr/share/X11/xorg.conf.d/90-monitor.conf
Section "Monitor"
Identifier "DSI-1"
Option "Rotate" "right"
EndSection
I used the following for rotating Touchdevice:
dtoverlay=vc4-kms-dsi-ili9881-7inch,dsi0,swapxy,invx
There is a small difference to the posting from @jmstone . Its because i mounted my display rotated to right.
Option Rotate right is invx
Option Rotate left is invy