How to reduce the size of the title bar in avada?

Have you asked the developers of your commercial theme?

https://themeforest.net/item/avada-responsive-multipurpose-theme/2833226

We don’t have access to them so don’t know how they are set up – so help here is generally limited to general WP questions. And without a link to your site, really no way to help much at all.

https://codex.www.ads-software.com/Forum_Welcome#Commercial_Products