A folder with sub-pages is not automatically creating a drop-down on my site header

Site URL: https://www.becnet.org

I went through the chat help and they directed me to the forum. I just added a new folder to my organizations webpage for events because I want to have dedicated subpages for each of our annual events because I want our annual events to have dedicated pages as dropdown items from the site header. However, these are showing up in my site header rather than as dropdown like my other folders. The chat help person found that in "Design>CSS" we have a custom code that appears to be the problem. The person who originally designed this website is no longer an employee here (and I had no idea they even knew anything about custom coding) so I don't even know what/why this custom code is added here in the Design section. Please help me figure out if I can/need to just delete this custom coding and/or edit it so that I am not having this issue with the Events folder subpages showing up in my site header rather than as dropdown items. Thank you!

.header-actions .header-nav-item {
  padding-right:1vw !important; /**change as needed**/

}

.header-nav-list   {
  display:-webkit-box;
  display:-ms-flexbox;
  display:flex;
  -webkit-box-pack:end !important;
      -ms-flex-pack:end !important;
          justify-content:flex-end !important;
  .header-nav-item {
     padding-right:1vw !important; /**change as needed**/
  }
}

.header-actions--right {
  display:-webkit-box;
  display:-ms-flexbox;
  display:flex;
  -webkit-box-pack:justify;
      -ms-flex-pack:justify;
          justify-content:space-between;
}

.header-actions .header-nav-item {
  padding-right:1vw !important;//change as needed

}

.header-nav-list   {
  display:flex;
  justify-content:flex-end !important;
  .header-nav-item {
     padding-right:1vw !important; //change as needed
  }
}

.header-actions--right {
  display:flex;
  justify-content:space-between;
}

.header-display-mobile .header-nav-item.header-nav-item--collection {
display:none;
}

Can you add & let me know? We can check problem easier

If the site is live, you can duplicate site & do on it.