WordPress Mega Menu Header Fix affecting the header banner

My site runs on WordPress and relies on a mega-menu plugin. Since the last update the header styling has slipped out of line—colors, spacing, and general layout no longer match the theme. I need the styling brought back to spec and, most importantly, coded in a way that survives future plugin or theme updates.

You are free to work directly in a child theme, custom CSS/JS, or a lightweight must-use plugin—whatever keeps the fix update-proof—but please avoid hard-editing core or vendor files. The goal is a clean, maintainable solution that restores the mega menu’s appearance across desktop and mobile breakpoints.

Please respond with a brief note highlighting similar WordPress header or menu fixes you have handled. I am especially interested in cases where you delivered a permanent, update-safe solution.

Deliverables
• Restored, responsive header styling for the existing mega-menu plugin
• Code isolated in a child theme or other update-safe location
• Short hand-off document outlining what was changed and how to adjust it in the future
- Fix the header mega menu / header banner