How do I limit sub-pages for a parent in the nav bar

I have a few tabs in my main navigation bar that have sub pages listed under them. As the site has grown there are many sub pages now and when the parent tab is hovered over the sub pages list all the way down the page. I think it has something to do with ‘depth’ or ‘wp_list_pages’ but can not figure out where to change the values to get what I want, just 3 or 4 sub pages listed at a time. My site is: https://www.indiebandguru.com I am using the Prosumer theme and do not know anything about changing CSS. The tab I am having a problem with is the articles tab. Any help is greatly appreciated.