Mobile menu help or plugin suggestion?

I am jumping into a pre-existing site build where are the client has only had standalone pages, but I am being asked to make a multi-page site.
I am stuck using Upper Theme’s Carbon theme (not a fan; horrible documentation) with WPBakery.

The menu options are very limited and don’t address mobile, but will convert to a hamburger on mobile thank goodness. However, the mobile menu is stretched unnecessarily across the screen and left aligned.

How do I fix this or do you have a recommendation for a menu plugin that’s free, simple, and good for desktop and mobile?

 

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