Excerpt text size: How to customize?

Site URL: http://www.bystoy.no

Hello! 

The Excerpt-text to my blog posts are pretty small. I´ve tried to to go Design --> Fonts and changed both Heading and Paragraph size, but nothing works. How do I get the text bigger in size? 

Thanks! 

I don't see excerpt. can you take screenshot?

The small text is excerpt-text. It´s blogposts without pictures. 

12 minutes ago, Ludvig said:

The small text is excerpt-text. It´s blogposts without pictures. 

Add to Home > Design > Custom CSS

div#block-yui_3_17_2_1_1588578805299_10384 .summary-excerpt p {
    font-size: 20px;
}

There we go! 

Thanks alot!