Question

Why is our weight 0 at centre of earth?​

Answer 1

$\huge\star{\underline{\mathfrak{Answer}}}$

Not only because there is no gravitational force down there but because at the center you will be completely surrounded or enveloped by earth, as a result you will be pulled by equal forces in all directions. Hence all the gravitational force lines will cancel out each other leaving you with zero net force.