how to define a numerical vector derivative in my Newton-Raphson code?

i wrote this code and because of my variable is numerical and a 3*1 vector, i had to wrote my derivative function as the "DERIVATIVE1" function that i attached here. the poblem is my derevative function makes complex numbers, but the derivation's numbers have to be real number. and another problem is my answers do not converge on the right answers. the main file is "Functional_Test_1"