Magento Speed Performance Optimization

We are looking for a company or individual that has knowlege and experience in Magento Performance [login to view URL] magento website is very slow. We want to improve the overall speed. Please don't bid if you are not skilled at it. Current megento website speed: - Server respond speed(First byte) over 3s to 4s - Maximum Full load time around 20s. Repeated load time: 13s - Deteailed test result: [login to view URL] What we have done: - 95% images are optimized with the extension apptrain image optimization - Redis installed on sever as backend cache and session handling - Opache installed and configured - Css and Js merged from magention admin system setting For your information: - Magento version: 1.9.2.2 with latest patch - Php 5.6 - Mysql 5.6 - Apache 2.0 - SSL not installed - Latest ultimo theme - 3rd party extension including ebizmart, gainpoint reward point, detailed review etc. - Server: digitalocean VPS: 4G ram; 2 core CPU. Memory consumption below 30%. - One domain with two stores - One language Our requirments/Goals : 1, Server response time (First byte) below 0.5s even for the pages with the most content such as this product page: 2, Full load time below 4S even for pages with the most content. Website Targets region: Europe and US 3, Google speed insight score over 95 4, wegpage speed test score AAAAA 5, Gtmetrix score over 95% 6, Explantion about what you have done to improve the speed. Because we want to know which parts were changed to avoid troubles or conflicts for future upgrade 7, Privacy protection: don't mention our website or related information on the internet. 8, optimaztion should be finished in 2 days . It's very urgent. 9, Keep all current website functions. Don't mess up the design and functions. 10, No other paid extension or additional service fees for this job. 11, Assistance of SSL installation. (SSL certificate already bought) 12, Sever safety configuration: don't compromise the server during optimaztion. Make the sever as safe as possible with all necessary settings. What confused us: - After enable cache from Magento admin, the site speed become slower. We see no improvement for repeated views. What we are worried about: - How to do this ? Can you work on the current server? Or we build a new server for your testing purpose? - How to keep our website safe( data and all info) during the testing ? It's very urgent. We will decide in 2 days. Please contact us with all the detailed information as soon as possible.