CSS / Mobile Responsive issue fixed in eBay Store

I have a very small project that I need help with - it is a CSS / Mobile Responsive issue in eBay with my store pages.

I have hardcoded the pages and they validate fine with WC3 and look good when debugged with Chrome.

I have the following issues that need to be fixed please:

1. My Store Home page has a horizontal scrolling issue in mobile devices.
2. My Header will not resize in Gallery View and the page is not mobile responsive
3. My Custom pages are not mobile responsive

I require someone to make small changes to my existing HTML and CSS coding - I do not want completely new coding or external CSS and javascript added.

This is a small easy project that requires a few small CSS changes / Media Queries looked into - NO STUPID PRICES OR FOOLS PLEASE!