The problem is that you actually are including the select
four times.
Infact, if you have a look into the navigation menu you'll see
<nav>
<nav id="menu">
<ul>
<li><a href="index.html">Home</a></li>
<li><a href="#">Bio</a>
<ul>
<li><a href="biography.html">Biography</a></li>
<li><a href="repertoire.html">Repertoire</a></li>
</ul>
</li>
<li><a href="#">Gallery</a>
<ul>
<li><a href="media.html">Media</a></li>
<li><a href="photos.html">Photos</a></li>
</ul>
</li>
<li><a href="agenda.html">Agenda</a></li>
<li><a href="contact.html">Contact</a></li>
</ul>
<select><option selected="selected" value="">Go to...</option><option value="index.html">Home</option><option value="#">Bio</option><option value="biography.html">Biography</option><option value="repertoire.html">Repertoire</option><option value="#">Gallery</option><option value="media.html">Media</option><option value="photos.html">Photos</option><option value="agenda.html">Agenda</option><option value="contact.html">Contact</option><option value="https://www.facebook.com/elenacostasoprano">
</option><option value="https://twitter.com/elenacpsoprano">
</option><option value="https://www.youtube.com/channel/UCoRkjY7OEQFSs7KwmruUVPw">
</option><option value="https://plus.google.com/u/0/115736588985404106684/about/p/pub">
</option><option value="https://www.instagram.com/elenacostasoprano/">
</option><option value="contact.html">EN</option><option value="de/kontakt.html">DE</option><option value="es/contacto.html">ES</option></select></nav>
<nav>
<select onchange="window.location.href=this.value;">
<option value="index.html">Home</option>
<option value="biography.html">Biography</option>
<option value="repertoire.html">Repertoire</option>
<option value="media.html">Media</option>
<option value="photos.html">Photos</option>
<option value="agenda.html">Agenda</option>
<option selected="selected" value="contact.html">Contact</option>
<option selected="selected" value="">Go to...</option><option value="index.html">Home</option><option value="#">Bio</option><option value="biography.html">Biography</option><option value="repertoire.html">Repertoire</option><option value="#">Gallery</option><option value="media.html">Media</option><option value="photos.html">Photos</option><option value="agenda.html">Agenda</option><option value="contact.html">Contact</option><option value="https://www.facebook.com/elenacostasoprano">
</option><option value="https://twitter.com/elenacpsoprano">
</option><option value="https://www.youtube.com/channel/UCoRkjY7OEQFSs7KwmruUVPw">
</option><option value="https://plus.google.com/u/0/115736588985404106684/about/p/pub">
</option><option value="https://www.instagram.com/elenacostasoprano/">
</option><option value="contact.html">EN</option><option value="de/kontakt.html">DE</option><option value="es/contacto.html">ES</option></select>
<select><option selected="selected" value="">Go to...</option><option value="index.html">Home</option><option value="#">Bio</option><option value="biography.html">Biography</option><option value="repertoire.html">Repertoire</option><option value="#">Gallery</option><option value="media.html">Media</option><option value="photos.html">Photos</option><option value="agenda.html">Agenda</option><option value="contact.html">Contact</option><option value="https://www.facebook.com/elenacostasoprano">
</option><option value="https://twitter.com/elenacpsoprano">
</option><option value="https://www.youtube.com/channel/UCoRkjY7OEQFSs7KwmruUVPw">
</option><option value="https://plus.google.com/u/0/115736588985404106684/about/p/pub">
</option><option value="https://www.instagram.com/elenacostasoprano/">
</option><option value="contact.html">EN</option><option value="de/kontakt.html">DE</option><option value="es/contacto.html">ES</option></select></nav>
<div id="extras">
<div id="socialcontainersup">
<p>
<a title="Follow me on Facebook!" href="https://www.facebook.com/elenacostasoprano" target="_blank">
<img style="margin-right:0px; margin-left:0px;" src="images/facebookmovil.png" onmouseover="this.src='images/facebookmovilhover.png'" onmouseout="this.src='images/facebookmovil.png'" alt="Facebook" width="32" height="32"></a>
<a title="Follow me on Twitter!" href="https://twitter.com/elenacpsoprano" target="_blank">
<img style="margin-right:0px; margin-left:0px;" src="images/twittermovil.png" onmouseover="this.src='images/twittermovilhover.png'" onmouseout="this.src='images/twittermovil.png'" alt="Twitter" width="32" height="32"></a>
<a title="Subscribe to my YouTube channel!" href="https://www.youtube.com/channel/UCoRkjY7OEQFSs7KwmruUVPw" target="_blank">
<img style="margin-right:0px; margin-left:0px;" src="images/youtubemovil.png" onmouseover="this.src='images/youtubemovilhover.png'" onmouseout="this.src='images/youtubemovil.png'" alt="Youtube" width="32" height="32"></a>
<a title="Follow me on GooglePlus!" href="https://plus.google.com/u/0/115736588985404106684/about/p/pub" target="_blank">
<img style="margin-right:0px; margin-left:0px;" src="images/googleplusmovil.png" onmouseover="this.src='images/googleplusmovilhover.png'" onmouseout="this.src='images/googleplusmovil.png'" alt="GooglePlus" width="32" height="32"></a>
<a title="Follow me on Instagram!" href="https://www.instagram.com/elenacostasoprano/" target="_blank">
<img style="margin-right:0px; margin-left:0px;" src="images/instagrammovil.png" onmouseover="this.src='images/instagrammovilhover.png'" onmouseout="this.src='images/instagrammovil.png'" alt="Instagram" width="32" height="32"></a>
</p>
</div>
<div id="language">
<span class="langswitcher">
<a class="active" href="contact.html">EN</a>
|
<a href="de/kontakt.html">DE</a>
|
<a href="es/contacto.html">ES</a>
</span>
</div>
</div>
<h3>Contact</h3>
<select><option selected="selected" value="">Go to...</option><option value="index.html">Home</option><option value="#">Bio</option><option value="biography.html">Biography</option><option value="repertoire.html">Repertoire</option><option value="#">Gallery</option><option value="media.html">Media</option><option value="photos.html">Photos</option><option value="agenda.html">Agenda</option><option value="contact.html">Contact</option><option value="https://www.facebook.com/elenacostasoprano">
</option><option value="https://twitter.com/elenacpsoprano">
</option><option value="https://www.youtube.com/channel/UCoRkjY7OEQFSs7KwmruUVPw">
</option><option value="https://plus.google.com/u/0/115736588985404106684/about/p/pub">
</option><option value="https://www.instagram.com/elenacostasoprano/">
</option><option value="contact.html">EN</option><option value="de/kontakt.html">DE</option><option value="es/contacto.html">ES</option></select></nav>
where there are four select menu that are shown using this media query
@media only screen and (max-width: 600px){
nav ul { display: none; }
nav select { display: inline-block; }
} /*Note: This last bracket miss in the original css*/
which basically means "Hide every ul
and show every select
element placed inside a nav
element".
To resolve the issue, you can just get the rid off of every select
but one.
Please also notice that there are several error both in the html and in the css.
Use a validator to help you find those issues and correct them. There's plenty of them online, like this one (for CSS)
Best!