Different in the pages. Reduce to one

Hello, I hope you can help me with this h1 matter. When I search for h1 more that one h1 show up. How can I eliminate those ones: (1) <div id="site-header"> <h1 class="site-title"></h1> <h2 class="site-description"></h2> with no content and (2) <h1 class="assistive-text">Primary Menu</h1> Maybe the class has to stay? Thanks so much for your help. Best regards Petra