Hi @sultaan You could use the HTML inspector to locate the product title and then set a css rule - for example ("font-size: 15px;"). I have a video (https://youtu.be/z_mu45rbpeM) talking about how to change the font styles for Shopify store webpage, you may find the elements in the video are different, but the idea is the same. You can easily do it by yourself.
Couldn't do it, my friend! I'm not able to find the product title text-size in the inspector.
Could you please share your store URL and password, so I can take a look? Thanks