Geeetech

i got a Geeetech Dual Extruder Prusa i3 pro C
and i dont get the Extruder to work propper i need to hand feed the filament to get a calabration cube if i dont hand feed the filament i will get a cone insted of a cube.
an i got a gt2560 bord

1) Which firmware do i need ?
2) wher do i download ?
3 ...

me to pls