Hi! Im new here and I have a question.
How can I fix this error?
Im trying to fix it changing the tiling and offset , but they change all walls , and I want only change one.
Thanks!!
Have you built this out of Unity Cubes?
If so that is the underlying issue. You can work around this by creating a new “Material” and applying the same shader to it. Now select the same texture in this shader on the new Material. Now place this new Material on the central block and adjust the tiling property on it, which will now be independent.
Note that this is not a good way to do this, you are better using something like Blender to build your 3D models(objects) in. Done properly you can “unwrap” the object in a way that avoids issues like this. It is also better for performance as you will need two Materials for the quick fix solution and only one when done properly. Do not worry about this too much yet, for now the quick fix will suit you fine. I mention this as a nudge in the direction you should take when you feel ready 
you should Create a new material for middle wall thats it
If those blocks for some reason are different objects: In Blender:
-Select the cubes (might have to do it one by one)
-Apply the scale by hitting Ctrl-A and then choosing scale in the pop-up menu.
-Enter edit mode, select all, Unwrap (U-key), choose cube projection which works fine for tileable textures.
This should make them all have the same scale of the texture. If the scale is not what you desired, adjust the tiling settings in the material and it will apply evenly to all the cubes.