Hi Marcell-
Generally speaking, you’ll change these in your Customize > Fonts > Headings menu.
If you want to only change the font on those specific pages, you’ll need to use Custom CSS to do so. Since each page and post has a unique class for the <body> tag, you can use the page’s ID to accomplish this, or in the case of your blog page, the blog
class.
Navigate to Customize > Advanced > Custom JS & CSS and use CSS rules similar to this:
body.blog h2.widget-title, body.page-id-560 h1.entry-title a {
font-family: 'Open Sans';
}
This is based on the Page ID for your /portfolio-de-investimentos/ page, which is 560. You can replace 560 with the ID of any other page if you need to use this rule for other pages.