Good day!

*WARNING bad english ahead, it's not my native language*

I've just got a new 3D printer, a FLSUN Prusa i3, and I have some really bad problem with it.

I use Repetier, Arduino, Marlin and an autoleveling sensor

Since I've installer Arduino and Marlin, my Z axis won't go down when I press the Z HOME or the MAIN HOME (for X, Y and Z).
If I press the Z HOME, the hight increass of 2mm and the MAIN HOME increass the hight of 7mm then both reset the hight to 0.
If I increass the hight, without pressing the Z HOME or MAIN HOME, I can lower it with the software.
If I press one of the HOME I must lower it manually because REPETIER don't allow you to go bellow 0.

Before installing Arduino & Marlin I had no problem except for my LCD screen that I wasn't able to go in and it still not working...
If I was pressing the MAIN HOME, every axis was going at HOME, the Z axis was lowering, touched the plate then going 2mm higher and the extruder was going in the midle of the plate.

The firmware I had on my sdcard can be found here:

PLEASE can you help me?