Thank you all for your advice.
Sorry for mixing up RF terms. On my hardware and in Domoticz it is called RFXCOM - RFXtrx433 USB 433.92MHz Transceiver.
For me as a beginner it's hard to understand you recommend an extra micro controller and an extra long range antenna instead of fixing it by software. But if that is the case, I have to deal with that 
.
Thanks again!
@yveaux Yes, actually that was the plan having Domoticz and MySensors integrated. But what is my beginner mistake?
I have installed the Raspberry version of MySensors on the same Pi as Domoticz is running. In this Pi the RF-link antenna is plugged in the USB port, see this picture of my fuse box.
Actually I'm not primary interested of controlling MySensors, my main goal is using Domoticz for collecting sensor data and sending messages. So just 'sniffing' the RF signals.
Edit: RFlink
Thank you for your suggestions.
I don't have any wires nor pin connections as the RF-link is an USB module (RFXcom.
I understand having a controller and gateway separately is recommended. But I'd like to use the long-range antenna currently operational. Am I correct I can configure the MySensors in the same frequency of 433 MHz?
Could my error lie within the ./configure command?
After playing some time with sensors and Arduinos I read about MySensors I wanted to expand my home automation system with it.
Situation:
Raspberry pi 3 with Domoticz with RF antenna and Z-wave running for about 3 years.
Wish:
Connect sensors in the bee hives in my garden to a new topic in the MQTT database of Domoticz. I have a long range RFXcom antenna working on 433 mhz. MySensors is supported
Attempt:
./configure --my-gateway=mqtt --my-controller-ip-address=192.168.0.176 --my-mqtt-publish-topic-prefix=mysensors-out --my-mqtt-subscribe-topic-prefix=mysensors-in --my-mqtt-client-id=mygateway1 --my-port=/dev/ttyUSB0 --my-rfm69-frequency=433
Error:
Dec 28 23:55:49 INFO Starting gateway...
Dec 28 23:55:49 INFO Protocol version - 2.3.2
Dec 28 23:55:50 DEBUG Serial port /dev/ttyUSB20 (115200 baud) creat
ed
Dec 28 23:55:50 DEBUG MCO:BGN:INIT GW,CP=RNNGL---,FQ=NA,REL=255,VER
=2.3.2
Dec 28 23:55:50 DEBUG TSF:LRT:OK
Dec 28 23:55:50 DEBUG TSM:INIT
Dec 28 23:55:50 DEBUG TSF:WUR:MS=0
Dec 28 23:55:50 DEBUG !TSM:INIT:TSP FAIL
Dec 28 23:55:50 DEBUG TSM:FAIL:CNT=1
Dec 28 23:55:50 DEBUG TSM:FAIL:DIS
Dec 28 23:55:50 DEBUG TSF:TDI:TSL
Dec 28 23:56:00 DEBUG TSM:FAIL:RE-INIT
Dec 28 23:56:00 DEBUG TSM:INIT
Dec 28 23:56:00 DEBUG !TSM:INIT:TSP FAIL
Dec 28 23:56:00 DEBUG TSM:FAIL:CNT=2
Dec 28 23:56:00 DEBUG TSM:FAIL:DIS
Dec 28 23:56:00 DEBUG TSF:TDI:TSL
Who can help me here please?