Ok, I partly fixed my issues and I hope this will help.
So basically I haven’t figured out that i needed to add dtoverlay=ads7846 in the display config box.
My current working configuration is the following:
display= Generic hdmi display
config:
disable_overscan=1
display_hdmi_rotate=2
dtoverlay=ads7846,penirq=25,speed=10000,penirq_pull=2,swapxy=1,xohms=150
everything else as default.
I also found helpful to install and configure the touchscreen as described here, as the solution provided in this post was not working for me.
One step further.
External usb Audio and midi next.