ESP32_LoRaWAN TTN decoder issue

Hello all, I’m pretty new to The Things Network in conjunction with Heltec LoRa nodes. I’m using the ESP32_LoRaWAN sketch for OTAA with The Things Network. I’m having a hard time understanding the bytes portion of the sketch. For example, I’m sending the latitude, longitude, and altitude of a gps module connected to my LoRa ESP32.

Im not sure how to format my sketch correctly send my data to my Gateway on the things network and how to decode it once it’s there.

You can reference this file.