Your description completely contradicts what the code (what there is of it) is actually doing.
TEMP_OUT_H/L 16-bit temperature data (2’s complement format) (result and result)
Ahhh. your comment is wrong, it should say:
TEMP_OUT_H/L 16-bit temperature data (2’s complement format) (buff and buff)
result = ((buff << 8) | buff) + g_offx;
The sensor values are read one byte at a time and have to be reconstructed into a 16-bit integer. result is a 16-bit number which is constructed of buff as its high-order byte and buff as the low order byte. The result is a signed twos-complement 16-bit integer which you can print as Serial.println(result).
You don't need to convert to decimal, Serial.println does that for you. Internally, Arduino's integers are 16-bit twos-complement anyway.