Hello @4711engel some recomendation is to use the Cayenne LPP data format. Find here more information Cayenne Low Power Payload | myDevices Documentation
Having said that, if you use the Cubecell find here an example to send data using LoRa → CubeCell-Arduino/LoRaWan.ino at master · HelTecAutomation/CubeCell-Arduino · GitHub
if you use the Arduino UNO, get a hat with WiFi, cellular, LoRa connectivity and try to send data to your IoT platform.
Let me know if that works 