Wordpress Site optimisation

I need someone to
1] Create a test/development version of my existing wordpress site on the same hosting service (a subdomain)
2] Clean up and optimise the coding of the site to improve website performance.
3]Measure the performance improvement on the original Vs the new Test version of the site. to Confirm the impact (current site has 3 to 5 Secs pages loads ... it should be sub 0.5 Secs
4] Copy the improved version to replace the original Site
Our site is Care24seven.com
A fixed price is required ... 50% deposit 50% when new faster version is up and running.
Only Wordpress web developers with strong references should apply.
And speed to solution in important.
Thanks