error finishing read!

No, I am already pinging from 192.168.1.120 to 192.168.1.121. In the text, I accidentally copied the IP from the PCW instructions. The ping works, it is probably a latency problem.

Sorry, missed that, no idea how but probably lack of sleep.
The 9.4nS time is way to much, there is another topic with similar results, so can you try this:
-click on "routen"
-check the "use this connection only for resources on this network"
-click OK
-click "save"
-close
-click on the network manager icon and click on "wired connection 1"
-pins as advised by PCW

Thank you very much, I will give it a try later.
Unfortunately, I can't evaluate the result of the ping and the histogram.
Which value is too large and how large should it be? best regards

Your fist screenshot above (with the correct address ) shows on the last line the min/avg/max/mdev values, the max value is above 9.4.
Please do this ping test again after all the above clicks and report back, it would be helpful if we can pinpoint what causes such high network latency.
Thank you.

I have run the long ping test 3 times. Here are the 3 results for max:
First ping test: 4.2ms 
Second ping test : 3.4ms
Third ping test: 15.9ms

So it didn't get any better.

Above in the attachment I had shown file /etc/network/interfaces.
There I had inserted lines for eth0 as described in man hm2_eth. Do I have to replace eth0 with enp5s0?

Greetings Anton

Did you do the network manager stuff?