To search engines, information from the title, descriptions and heading tag (h1) of a website are very important to understand the content of the page itself. So it's not very helpful to have more than one h1 headline per page. Keep it simple, use just one h1 per page and don't confuse search engines.
When you have access to the websites backend and you are able to edit, or to code in your template it should be easy to change your headline concept. When you are using Content-Management-Systems (CMS) like WordPress or Sparespace or others it's a little bit more difficult to change the headline concept. CMS are using templates. The creator of a template decides how many h1's are included per site.
If you have the knowledge and experience you can edit your template and change the spare h1 to h2 or h3 as you like. To get an idea about your headline concept you can use the RYTE Single Page Analysis. It shows how many headlines are used, which content they have and the hierarchy or respectively the order of the headlines. This is really useful to understand how your headline concept is designed.
When you don't know how to edit your template you should reach out to a developer or designer. They should be able to fix the headline concept.
Here is an interesting link about Common SEO Mistakes and How You Can Fix Them.