HTML Dropdown & Tracking Integration

I run a 40-page static HTML site and would like a hand streamlining three small but important updates. The pages already load quickly and look fine on mobile, so I’m hoping to keep that lean feel while adding a little more functionality.

Here’s what I need done:

• Navigation – Standard-style dropdown menu. Server-Side Includes (SSI) would be ideal so I can update the menu once and have the change ripple through all pages, but I’m open to any cleaner solution you can suggest.
• Google Ads – I’ll send over my ad container snippet; it just needs to be placed in the appropriate spot on every page without disturbing layout or speed.
• Google Analytics – Likewise, I already have the GA tag. Drop it in site-wide so tracking starts immediately.
• Responsiveness – Pages must remain mobile-friendly after the changes.

Code expectations
Clean, well-commented HTML/CSS (or SSI where relevant) that stays SEO-friendly, lightweight, and easy for me to tweak later. No bloated libraries—vanilla solutions preferred unless you can show a clear advantage.

If this sounds straightforward to you, let me know your timeframe and a fair price. I’m happy to zip the site over so you can see the structure before committing.