I try to add a pbr map right now and I need to add a image texture for that. I plugged the color imput of the image texture into the base Color of the Principled BSDF note. I also unwrapped the plane. As you can see in the picture no texture get shown up in the render. On the 3D view you also can see the material. But why does it not get rendered?
You are plugging a shader node (the Principled BSDF node) into another shader (Diffuse BSDF node). This is not how Cycles' shaders work. You should remove the Diffuse BSDF and things will start working.
Blender tries to imply you shouldn't do this by colouring the node sockets differently. A green output (indicating a 'shader') shouldn't be plugged into a yellow input socket (colour data). However, a green shader output socket should be plugged into a green input socket.
You can read more about node socket types here: