Hi Thanks for the advice.Finally figured out by debugging with println in method DFRobot_mmWave_Radar::readN

that available was false.

Finally found cold solder joints on my side. 

@Uwe.Raatz:Thanks for the feedback. You got pretty far and I understand the frustration. I'm still struggling with the communication. If I have some progress I let you know.  

Thanks for the feedback. I'm a newbie.So I don't understand what to do with this.Can you explain?

Sorry to break into conversation:@Uwe.Raatz: Di you manage to get it running?

Thanks for a feedback