WordPress automatically displays a toolbar at the top of the page when you’re logged in. Whether you view the WordPress dashboard or the front page of your site, it’s still there – and for many people it’s an annoyance.
Remove the Admin Toolbar with Code
If you would like to remove the toolbar with code, just drop the following snippet into your functions.php file:
add_filter('show_admin_bar', '__return_false');
This code will stop the toolbar from display on the front-end of your site.
There is easy way to remove it by using plugin. Just install and activate it on the site of your choice.
There have a lot of plugins help you do it such as
https://wordpress.org/plugins/hide-admin-bar/
Hope this can help.