How to remove default font and add custom fonts

The code for the Google fonts will be located in your functions.php file –

wp_enqueue_style( 'google-fonts', '//fonts.googleapis.com/css?family=Open+Sans:300,400,600,700', array(), CHILD_THEME_VERSION );

They are also in the style.css, but once you remove the code in the functions it should deactivate it from appearing on the site.

body {
	background-color: #fff;
	color: #333;
	font-family: 'Open Sans', sans-serif;
	font-size: 20px;
	font-size: 2.0rem;
	font-weight: 300;
	line-height: 1.625;
	margin: 0;
	overflow-x: hidden;
}

/* ## Headings
--------------------------------------------- */

h1,
h2,
h3,
h4,
h5,
h6 {
	font-family: 'Open Sans', sans-serif;
	font-weight: 300;
	line-height: 1.2;
	margin: 0 0 20px;
}

I’ve only used Google fonts and Typekit fonts. To upload your own fonts you may need to install a plugin or a follow a tutorial to set up your own. Here is an example tutorial – https://wpsites.net/web-design/custom-fonts-wordpress-font-face-generator/