Hey Julian!
Jake here from the SHopify guru team :)
Sounds like the code that was inserted into your theme when Yotpo was installed has not been removed. Usually this is in the theme.liquid and product.liquid of your theme's HTML. Head into Online Store > Themes > "..." button > Edit HTML/CSS to get to those theme files.
If you're having trouble finding the code, use Command+F (on a mac) or CTRL+F (on a PC) to do a word search for yotpo, and that should get you to where the code is.
If you're still having trouble removing Yotpo completely, you can reach out to their app's support team for more help!
1 (646) 977-7959
Hope that helps!
Regards,
-Jake