How can I speed it up because it's super slow

looking for same question. but i have super fast

You may now easily change the speed in the upcoming version of the plugin. Please take a test-drive the plugin:
https://github.com/BlogSynthesis/jquery-smooth-scroll/releases/download/1.3.0/jquery-smooth-scroll.zip

You will need to edit the file jss-script.js in the above beta release. Change the number in the line:
var scrollSpeed = 1500;

HTH,

Please ask your support related questions in WPAvenue Forums