Changing font size in child theme style.css

Hi,

So, i’m editing a Tiny-Hestia child theme’s styles.css to customise my site.

I can no longer edit the Typography section through Appearance > Customise as the section doesn’t let me click anything or use the sliders.

I am trying to change the font size across my site (navbar, headings, post body etc). So far, all i’ve been able to change is the title font of my blog posts.

This is the code i have relating to font in my style.css

/*navbar colour and navbar menu text colour*/

	.navbar{  
		background:#818d89;
		color:black;
}

	.home .navbar.navbar-transparent{ 
		background-color: #818d89;
		color:black;
		padding-top: 5px;
}

/*Navbar hover colours*/

	.navbar-default .navbar-nav > li > a:hover, .navbar-default .navbar-nav > li > 
         a:focus{
   	 	background-color: #a8b6b1;
    	        color: #000000;
}

/* dropdown text colour and hover font size*/

	a, .navbar .dropdown-menu li:hover > a, .navbar .dropdown-menu li:focus > a, .navbar .dropdown-menu li:active > a, .navbar .navbar-nav > li .dropdown-menu li:hover > a, body:not(.home) .navbar-default .navbar-nav > .active:not(.btn) > a, body:not(.home) .navbar-default .navbar-nav > .active:not(.btn) > a:hover, body:not(.home) .navbar-default .navbar-nav > .active:not(.btn) > a:focus, a:hover, .card-blog a.moretag:hover, .card-blog a.more-link:hover, .widget a:hover{
		color:black;
		font-size: 15px;

/* change fonts for whole site here */

	.navbar-nav, .dropdown-menu, p, a {
		font-family: Constantia, "Lucida Bright", "DejaVu Serif", Georgia, "serif";
	}

/* change font size on blog post  headings */

        .card-title a {
        font-size: 50px;
}

I’ve tried adding “font-size:30px;” to all of them and nothing is working. Please can someone help me figure this out?

Thanks!