HE K280 Calibration

I have a HE K280 printer and new to this. 

First off, I homed the printer successfully, but whenever I tell it to go down -10 mm, it goes down really slow and it doesn't stop. I have a feeling this has something to do with Travel Feed Rate or Z Axis Feed Rate? 

And are there any other tutorials on how to calibrate it with a auto level sensor? No offense but the link here is a bit confusing/it tells me to go into the firmware, which I don't think I want to do unless its necessary. 

Thanks