z-index does not work with google adsense ad

I have a problem that is as follows.

I have a menu at the top with position fixed and a z-index of 99999. I put this ad but the problem I'm having is when I go down and I get the advertisement. The advertisement is in front of my menu. I've tried using lesser position than my menu but it did not help.

IMG Of the problem.

Ineedthisadtobebelowmymenu.

Adscript:

<scripttype="text/javascript">
                google_ad_client = "ca-pub-5653567333761325";
                google_ad_slot = "4495238327";
                google_ad_width = 336;
                google_ad_height = 280;
            </script>
            <!-- Anuncio_aside -->
            <script type="text/javascript"
            src="//pagead2.googlesyndication.com/pagead/show_ads.js">
            </script>