I would like to hire a WordPress Developer

We have a website already running on wordpress with bimer theme version 1.1 and some custom features, Now we want to update the theme to version 4.0 without losing any features of the site. Then we require some additional changes in theme design like adding share button at header bar, floating bar with share and next page button, layout change of posts body box, adding categories on homepage, adding image to top at 4 of our main category page, and a few minor changes. We require someone who is well experieced in playing with the codes, Not someone who do things just from plugins and using wordpress customization setting! Also who can make sure that website will remain light, and know how to speed up a website. If you'll provide good work and we have so many other projects pending as well. Please don't waste time if you are not well experieced, and use only plugins and shortcut ways. Thanks