CSS Issue: Trying to get my dropdown to center on the word its under + Transparency

Site URL: https://www.squarespace.com/templates/lusaka-demo

I am currently using Lusaka and was able to find out how to do transparency on the dropdown menu when hovering over the main header navigation. The problem is that the dropdown on this template does not center on the word that it is dropping down from.

Transparency code used

.header-nav-folder-content {
   background: rgba(0,0,0,0.3) !important;
}

The problem

The text has a huge box around it and its not centered on the dropdown items. I also wanted to get the "Getting Started" to be centered under "I'M NEW"

How would I go about fixing this while keeping my transparency?

Thank you for any help anyone can offer. Banging my head on the wall on this one. 

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