Hi,
I have real experience about how to Boost speed of website including Shipify, Wordpress, Mmagento, Joomla, Neto-eCommerce, Bigcommerce etc.
Also I have good 2 profiles in other freelancer sites. which are also related to website speed optimization.
I will test your site so please let me know site url, so I could let you know condition about your site.
I will manually apply server side changes via code, remove unused CSS / JS, compress (images, CSS, JS), gzip, Leverage browser caching, expire headers and remove some item under render blocking javaScript. So your site will open fast.
Please send me site admin login/pass so I could fix speed related issues and Hope you will agree to accept my changes to speed up your site.
I look forward to hearing from you.
Many Thanks.