Slidedown, up and toggle problem!

Slidedown, up and toggle problem!

Hi Guys!

I have a problem with jquery, I would like to use slidedown and up or toggle

my code

       <div class="vertical-termekek">  <ul class="nav nav-pills nav-stacked col-md-3 col-sm-12 col-xs-12" id="vertical-nav"><p>Termékek</p> <li class="dropdown">
 <?php 
wp_nav_menu(array(
  'container_id' => 'cssmenu', 
  'depth' => 3,
  'menu_class' => 'nav nav-pills nav-stacked',
  'theme_location' => 'secondary',
  'fallback_cb'       => 'wp_bootstrap_navwalker::fallback',
  'walker' => new CSS_Menu_Maker_Walker()
)); 
?></li>
</ul></div>


SCRIPT

$(document).ready(function() {
   $('.vertical-termekek').click(function () {
console.log ( "someButton was clicked" );
        $('li', this).slideDown(200);
});
});


Css

@media(max-width:768px) {
li.dropdown{
display:none;
}
}


Its working fine when i am full screen vertical menu not close is great i dont want to close vertical menu,by full screen 
but i would like to use jquery code when i go smaller screen (992px and smaller)

I don't know what is the next step!

If i go smaller screen no hide li class but work slide up and down

it used this because i have submenu too and anybody click submenu i don't wanna to close the hole vertical menu just accordion down

$(function () {
    $('.vertical-termekek').click(function () {
        $('li', this).slideToggle();
    });
    $('.vertical-termekek li').click(function(e) {
        e.stopPropagation();
});

//Resize handler to reset the menu visibility 
var resizeTimer;
$(window).on('resize', function (e) {
    clearTimeout(resizeTimer);
    resizeTimer = setTimeout(function () {
        if ($(window).width() > 992) {
            $('li.dropdown').show();
        } else {
            $('li.dropdown').hide();
        }
    }, 250);
});

});




but li class shown i couldnt' hide

and if i make 

Css

@media(max-width:768px) {
li.dropdown{
display:none;
}
}

the slidedown and up dont work (confusing)

and slide up and down work on full screen (its bad for me) I wanna fix during full screen

thx helps!