Nozzle and heating bed

The distance between the nozzle and the heating should be 0,25 mm when we have x=y=z = 0 on repertier-host ?

It should be 0.25 across the entire surface. But realistically, I try to measure 0.25 in the center of the bed, because that is where I print the most, and the edges (around/beyond the screws) usually have a bit more distance.

The thickness .25mm is the thickness of two euro notes. Place two new euro notes under the nozzle when it is in the front right (0,0). Turn the z axis screw by hand so that the notes just pull out from under then nozzle without any tension.
Slide the bed so that the nozzle is now over the right side of the bed.
Use the screw under the bed to adjust the bed so that the notes slide in and out with just the slightest tension.
Lightly tighten the lock ring under that corner.
Slide the bed to the the other way so that the left front of the bed is just under the nozzle,
do the same again with the euros, the slightest of pressure.
Continue in the same way with the back left,
the back right corners of the bed. The front of the bed is level left and right. now do the same with the back of the bed.
By the time you are done, all four corners of the bed will have the same tension on the euros, and each corner lock nut should be lightly tightened.
Check the last time with the nozzle and euro notes in the center of the bed.
Once that’s set, tighten all of the platform lock nuts.
Your bed should be level.

Now adjust the z end stop.
With the nozzle unmoved from the center of the bed, tighten down the stop until you hear the switch click.
Using the interface, pronterface or repetier, or your choice of interfaces raise Z then home the axis with
the euros in place, test for very slight tension by moving the notes back and forth.
If there is too much or too little friction on the notes, adjust the end stop screw a quarter turn at a time until when you home the Z axis the tension is just right.

-Not all plates, glass or metal, or circuit boards are flat. Don’t be discouraged.
-Don’t be discouraged flatness and alignment are an ongoing process, not a set it once and forget it task.
-If you take the Z axis screw and put the threaded part up, instead of down, as in the instructions, it is easier to adjust.
-A drop of cyanacrylate glue between the nut and the plastic adjusting disks may solve a lot of frustration as the the nuts and the disks want to go in separate directions when they are screwed too far and fall off the screws.
-When a platform is heated it has a different dimension than when it is cool. It is best to test the bed and adjust the z stop at the working temperature for your material.
-When I’m lazy I’ll print a skirt (see slic3r) and adjust the z axis by hand as the print starts so that there is a layer of material the same thickness all around, that is squished down and stuck down.

Good luck