Adding simple codes on fucntions.php we will be able to improve the score of Defer parsing of JS. We won’t need to access cPanel, instead can only work with the WordPress login credentials.
Additionally, plugins like Autoptimize, WP Rocket are also very good to improve the WordPress optimization speed.
However, we would like to remind you that GTmetrix is alone is not the factor that makes a website great, if you run a test of youtube.com on GTmetrix you can see how bad the score is, yet Youtube is an amazing site.
Here are other tutorials to improve your GTmetrix Score: