FINALLY!
My replacement arrived and I soldered it to my pro mini. This time I used a level converter for powering it directly from VCC and not the arduino's VCC. First no luck, but after switching MISO and MOSI it finally worked:
LED Flash
Checking LoRa Device
LoRa Device Present
LoRa device version 0x12
LoRa Registers
Reg 0 1 2 3 4 5 6 7 8 9 A B C D E F
0x00 00 09 1A 0B 00 52 6C AA 99 4F 09 2B 20 08 02 0A
0x10 FF 70 15 0B 28 0C 12 47 32 3E 00 00 00 00 00 40
0x20 00 00 00 00 05 00 03 93 55 55 55 55 55 55 55 55
0x30 90 40 40 00 00 0F 00 00 00 F5 20 82 EF 02 80 40
0x40 00 00 12 24 2D 00 03 00 04 23 00 09 05 84 32 2B
0x50 14 00 00 11 00 00 00 0F E0 00 0C F0 07 00 5C 78
0x60 00 19 0C 4B CC 0E 7F 20 04 47 AF 3F 7A 00 3B 0B
0x70 D0 01 10 00 00 00 00 00 00 00 00 00 00 00 00 00
Current frequency 434.666MHz
Write new frequency 434.400MHz
Changed frequency 434.400MHz
Seems like the diagram of the shop where I bought the arduino is switched. However I can now try to read the sensor and send the data via LoRa! Awesome!
One final question (not related to this issue but maybe you can still answer that in this topic ) : I got a RXB6 runnign to read a radio rain sensor at 433MHz. Is this received able to recive also LoRa signals or do I need a dedicated LoRa chip to receive LoRa radio signals?