More than an h1 in homepage

Hi, I created a child theme to change some sizes and colors and these chenges work. But I can't change the heading tag of the menu and section titles on the homepage. These titles are all in h1, but in this way each page has more than one h1. I tried to insert the modified functions into the file function.php of the child theme, but the titles remain in h1. Could you told me how can I make these changes using the child theme? Thank you! Martina