I want my Object to be one Meter long on the Z-axis. The Problem itself is a simple mathematical thing: When I tell the editor to move my object 1 meter up (so on Z axis 1.0 m) then it moves the center point (orange) 1 meter up, on which my object is fixed. At the same time, I want that my object has a length (also on the Z-axis) of 1 meter. But how is this possible (picture)?: My center point is in the middle, so if the orange point would be on the green y axis, then it would be Z 0. But how you see, I've already set it to 1 meter. But the object is 2 meters long. Which kind of wrong relation is that? Or did I make sth wrong? The distance between the orange point and Z 0 is 1 meter. But the end of my object is again 1 meter above the orange point so it is 2 meters long even though I typed in 1 meter? Please help me out. It really confuses me.
Try popping out the properties panel (it is a panel in the 3d view on the right, usually summoned with the N keyboard shortcut).
You may need or want to reset the scales to 1 in all axes. If you like the shape of your object but still want to reset the scale you can Apply Scale (ctrl-A is default shortcut for apply menu). As you can see from the screenshot the dimensions are different from the scale and from the location.
If you set the location first, and then the dimensions, the scale will be set appropriately for you.