Joomla Framework Update - To speed up our website

We have had issues with speed on our website and have recently hired a freelancer to optimise and speed up, however he could not do anymore due to a lot of third party JSS files. We want all of these files fixing and testing as soon as possible, our host has recently said the below: 'The contents of the website are at the maximum limit with respect to the platform (Joomla) used. So it is not possible for the website to optimize the speed if the contents(images and external JS) are not reduced. Since Joomla framework has limitations which are restricted for code modifications. So we recommend updating Joomla and use the best Joomla framework that suits your website. Best frameworks are as follows 1. Helix 3 Framework by JoomShaper 2. JA T3 Template by Joomlart 3. Gantry Framework by RocketTheme 4. Warp Framework by YooTheme 5. Expose Framework by ThemeXpert We need a freelancer who can do the above quickly and can suggest what else we can do to speed up the website and optimise across the board. We also need a full report on what has been done and clear evidence of the site being faster to load.