I started working for this company a week ago and the previous web dev had installed many unnecessary plugins no optimization at all. When i tested on google insights i got “30” on mobile and “70” on desktop.

On gt metrix the website had 5s load while the website is a simple service blog nothing hard back end work.

I checked on Dev tools and the website had 1.000.000bytes of un used CSS code and 300.000bytes of un used JS code.

Is there a way to remove the un used code from the website without me removing 10.000 lines of code manually? Or should i recreate the website from scratch, will rebuilding make it better if i remove all the existing files and build from scratch?