Redirect to login page in wordpress

Solution:

To redirect the user from homepage to login page, you can use WordPress function is_user_logged_in,

https://developer.wordpress.org/reference/functions/is_user_logged_in/

if(!is_user_logged_in()) {
    wp_redirect( wp_login_url() );
}

To redirect user on homepage rather Dashboard, you can follow already posted solution on Stack overflow.

https://wordpress.org/support/topic/how-can-i-redirect-users-to-the-front-page-after-log-in