In the attached file I would like to use the functions "Gradient" and "Hessian". Hessian should also calculate the determinant and check positive definiteness. I was unable to do that. Other questions for me as a beginner are:
How are the long brackets and the > sign on the left edge created? What does a semicolon at the end of the command mean? How is a 3D plot created? What does "restart" mean?

Regards, Alfred_FAF_20240831.mwAF_20240831.mw