What is the best way to comment in our code?

Today after 5 rounds of interviews, I got rejected because my code wasn't documented/commented on properly, although I have had, but apparently wasn't good enough. so what is the best way to do it? should I comment in the code briefly explain each block, or just prepare a separated pdf file and fully explain it there.

**just for an example I will leave some code here **
**ps feel free to point out my mistake on my code **

import React from "react";

import Classes from "../../container/Contact.module.css";

const Modal = (props) => {
  return (
    <div id={props.id} className={Classes.Success} onClick={props.clicked}>
      <span>Thank you for your intrest, We will contact you shortly</span>
    </div>
  );
};

export default Modal;