nano /boot/config.txt
after the last entry:
dtoverlay=ads7846,speed=500000,penirq=17,swapxy=1
Press Ctrl-X then Y to exit nano and save the changes.
nano /usr/share/X11/xorg.conf.d/10-evdev.conf
Section „InputClass“
Identifier „evdev touchscreen catchall“
MatchIsTouchscreen „on“
MatchDevicePath „/dev/input/event*“
Driver „evdev“
Option „InvertY“ „true“
EndSection
Press Ctrl-X then Y to exit nano and save the changes.