Adaptive version of the site, plus additional work!

The site was written on pure php + jQuery 10 years ago.
I was made an adaptive version under mobile devices with a new, so-called Sandwich menu.
The following works are also performed:
404 errors are correctly performed.
Create in the administration of an additional field form of editing/creation of articles;
Working forms through Ajax
HTML and CSS lines.
- Optimization of code and more...