I have created many different Layers filled with Objects.
Now I just realised that I worked von the XZ Plane all the time. For further work, it will be necessary that everything is perfectly paralel to the XY Plane. From the XZ I get to the XY by rotating 90 Degrees around the X - if im not wrong.
If somebody knows how to do that, I would appreciate any help!
Now I have my object in the correct plane (XY) but its facing the wrong direction, means I have to rotate it by 90 degrees around the Z - Axis. If i use the transforma and rotate 3D i can just manually rotate, but I want a rotation exactly by 90 Degrees around Z.