Hello,
I see that you use the paragraph tag for that title https://gyazo.com/7766a7b8165d2bc96b6cc4e95eba482c So, if you check “Use theme default font family?” it will use the font that you set for the body in theme typography settings. If you want to use another font then uncheck the tick and choose the font you need https://gyazo.com/5ac2efc4f5cf1cf7a1ee4ea8054bb722
Regards