Freelancer PHP Developer – Willing to Work on GIT or Desktop Sharing

Hello, I have websire made in PHP
It is slow and got some errors

I need to fix the following —

> Optimize CSS Delivery
> Minimize HTTP Requests
> Remove unused JavaScript
> On Website Large DOM Size (need to reduce) (4722 Elements)
> Minify and compress network payloads
> Apply route-level code splitting (minimize the size of your JavaScript bundles) (Minifying CSS files can reduce network payload sizes)
> Remove dead rules from stylesheets and defer the loading of CSS not used for above-the-fold content to reduce unnecessary bytes consumed by network activity
> Reduce Sever Response Time
> lazy loading
> Reduce Sever Response Time
> make long cache lifetime

I have an issue. I will not able able to share the codes. How else can we work ?