Change Fonts on child theme propuct listing and Main site product listing

Hope you are well,
I don't know exactly where I can change the font for header on the product listings.
I would like to change the font-family and font-size for the products, both in the main store and in the child theme GridMarket. The default is a much larger font than is I would like.

The font on the product description is also too small and hard to view. Second screen shot.

The product listings also don't align properly depending on the font size. Can you please provide the css in which can alter this.

regards,
Lisa