WordPress Developer Needed to Fix Header & Navigation Menu

I'm looking for someone who can help fix an issue with the header and navigation menu on my WordPress website. The menu was working fine before, but today it suddenly started causing problems. We tried to fix it ourselves, but unfortunately things got worse, and now the header isn't displaying properly either. I mainly need someone who can carefully troubleshoot the issue, restore the header and navigation menu, and make sure everything works properly on both desktop and mobile devices. I don't want the whole website changed—only the affected header and navigation area. Please keep the existing design, layout, and styling as much as possible. I'm looking for someone who can identify the root cause and fix the issue properly without affecting other parts of the website.