Setting up Z-Axis(GEEETECH i3 Pro W)after homing the Z-axis will be a large distance above the bed when starting a print

[medinseto]

Hi community, thanks to everyone who helped with my previous issue.
My current issue is the following:
after homing and leveling the bed to the height of the nozzle when at Z-Axis home all seemed well until i started a print.
the nozzle will then begin printing waaay too high above the print bed.

My Z steps/mm are 2560 on M8 lead screws, 1,8° steps with 1/16 microstepping (not sure on the terminology here i apologize), the repetier host calculator tells me this is correct. When i use the commands from the LCD screen to move Z by 1mm i can measure with a ruler that this is entirely off. How do i find out the correct amounts of steps/mm on the Z-axis? (also if anyone knows how to change that via repetier host would be great, because using the knob on the LCD to adjust that would take forever)