Rostock mini pro, problem with movements

Hello, I'm new here and also new to 3d printers.

I built a rostock mini pro with ramps 1.4.
for the software configuration i used these instructions: [onedrive.live.com]
after configurating the printer in repetier host i press the home symbol.
The carriages should move up until they hit the endstoppers, but that doesnt happen.
Instead the carriages just jump a few mm in some direction.

I hope you can help me out here, i checked the internet but couldn find anything...