How do I modify the font across the whole theme?

I find the font changes too much throughout, in size and weight. How can I modify it?

Is there a bit of CSS that will standardize things, which I can then modify?

Please and thank you!

 

Hello,

Paste this code in Custom CSS
Appearance > Theme Option > Styling Option > Custom CSS

Code:

 h1, h2, h3, h4, h5, h6{
color:red;
font-size:20px;
font-family:arial;
}
 
p{
color:red;
font-size:20px;
font-family:arial;
}

Thanks & Regards
Gourav Shrivastava