How to display login form anywhere, when user isn’t logged in, without redirecting?

I don’t know how theme my login works. You can do it manually by checking if an user is logged in or not:

if ( is_user_logged_in() ) {
    //user is logged in, put your regular codes
} else {
    //user isn't logged in, create a login template and call from here
    get_template_part ( 'content', 'login' ); //create your login form at content-login.php file
    //or you can use the wp built in function to load the default form
    wp_login_form();
}