function yourmodule_user_login($account) {
  // We want to redirect user on login.
  $response = new RedirectResponse("yourpath");
  $response->send();
  return;
}

<?php
/**
 * Implements hook_form_alter().
 */
function [MODULENAME]_form_alter(&$form, DrupalCoreFormFormStateInterfaceFormStateInterface $form_state, $form_id) {
  switch ($form_id) {
    // Alter login form and add own custom submit handler.
    case 'user_login_form':
      $form['#submit'][] = '_[MODULENAME]_user_login_form_submit';
      break;
  }
}

/**
 * Custom submit handler for login form.
 */
function _[MODULENAME]_user_login_form_submit($form, FormStateInterface $form_state) {
  // Set redirect to login form.
  $form_state->setRedirect('YOUR.MENU-ROUTER.NAME');
}