Create an anchor on forms so when a form is submitted without AJAX it return to the form.

nf-add-anchor.php

<?php
function nfjal_add_anchor_to_form() {
  echo '<div name="ninja-form-top"></div>';
}
add_action( 'ninja_forms_display_before_form_wrap', 'nfjal_add_anchor_to_form' );

function nfjal_add_anchor_to_url() {
  global $ninja_forms_processing;
  $url = 'http://YOUR_URL/#ninja-forms-top';
  $ninja_forms_processing->update_form_setting( 'landing_page', $url );
}
add_action( 'ninja_forms_pre_process', 'nfjal_add_anchor_to_url' );