Need Advice About Fade in Menu from Reviewer Soft Reject

Envato Authors Theme Authors
1

Hi, all!
Need some advice about secondary menu in my theme.

You can see it here, just click on the right top angle on hamburger button.

Here is print screen from reviewer: https://envato.d.pr/BZJF39

How do you think should I add some menu items? Or should I fill all negative space?
Or animation is too slow?

Thanks in advance.