Form RespondentEmail

Please avoid including 2 Questions within 1 Post to avoid any confusion.

Sample Code

var form = FormApp.getActiveForm();
const formResponses = form.getResponses();
for (let i = 0; i < formResponses.length; i++) {
  const formResponse = formResponses[i];
  console.log(formResponses[i].getRespondentEmail())
  const itemResponses = formResponse.getItemResponses();
  for (let j = 0; j < itemResponses.length; j++) {
    const itemResponse = itemResponses[j];
    Logger.log(
        'Response #%s to the question "%s" was "%s"',
        (i + 1).toString(),
        itemResponse.getItem().getTitle(),
        itemResponse.getResponse(),
    );
  }
}

What you need is to get Respondent Email in your case, please check the code above for the changes I made. I just console log it since I have no Idea.What is your next step. I answered this first because I do think that it affects the next step of your project. If you have further questions please post it as another question.

Reference:

getRespondentEmail