main menu page redirects to user ID

One solution would be to create a page with a page template that gets all info based on the user ID. Then you can add that page to the menu.
Something like this:

<?php
/*
 * Template Name: User Info
 */
 get_header();

 //Your code for getting the users id
 $user_id = '123';

 //Output userinfo using your code
 ...

This code shold be saved as a file in your theme folder. Name it something like template-user.php. Then when you create a new page in WordPress you can select this template as the page template.

To get your theme´s HTML structure easily, you can copy the content of your theme page.php and add it to this file.