Geeetech

Hi. I bought the i3 Pro B. I'm going through calibrating and setting up the printer. My X motor is running in the opposite direction. As per the manual it says to change in the firmware #define INVERT_X_DIR true to false. When upload the modified firmware I get an error. exit status 1
using typedef-name 'fpos_t' after 'struct'

I'm new to 3D printing and editing firmware. I followed the How to install the firmware for GT2560 thread with no luck. What am i doing wrong?