Data conversion failed from point to curve

Hello, I’m a beginner of GH,
I just wanted to make a brick wall but since that message appears, I can’t do anything after that
what’s the problem?!

Attach a file.

Same as you have to read in the Command line in Rhino when executing a Rhino command,
you need to read what the inputs and outputs are in Grasshopper.

Hover your mouse on the inputs / outputs!

In this case, Grasshopper tells you the following for the C output of the Contour component you chose:

If you hover over the C input of the Contour component, it says “Curve to contour”.

Your input is a surface, so something is wrong here.

If you want the contour curves of a surface, simply use the other Contour component.