hi,
I have been modeling the "brandenburger tor" and tried the whole day to find a good texture and to make it look realistic.
what is the best way to make it work, or where do I have to start reading again?
I have used psd
what do you mean by "make it work"? you mean map it to your building? it depends on what it looks like... if it's flat then you can use the planar mapping option and put the file as the shader's color. If it's not flat then... there are lots of ways to go about it.
Maybe i didn't answer your question, you gotta be more specific.
sorry for the missing details, it isn
get a digital camera and go take some pictures to create your textures.
However, you'll of course have to have improve your photoshop skills if you want to create some nice textures.
There are a few tutorials online if you google on making nice textures for 3d in photoshop, might be a nice idea to take a break from your project and try it out.
I would have to travel 900 km to take these pics, would like to but no time for it 
I think I will try it with photoshop and make some tuts there, thanks for the replies.
You can take pictures of materials anywhere.
What is it made of that makes it so special?
Brick is brick, wood is wood, sand is sand, concrete is concrete, metal is metal
you have to paint off the base to make it the way that matches what you're creating.
Hardly is there a project where the person had texture photos from the thing they are creating.