How to get only one h1 in my pages ?

Hello, I'm currently improving my SEO score and I notice that all my page have two H1. It's very bad for my SEO. I checked the source code and I saw that there is one H1 generate by the theme... <header class="entry-header"> <h1 class="entry-title">Blog</h1> </header> And the second one is the one I manually add in my page. I would like to delete the one generate by the theme. I don't want to use a CSS snippet because from the Google robot point of view, there are still two h1. Can I have another solution please? Many thanks in advance.