Website speed is decided by a handful of things that matter far more than any single plugin. The first is hosting: a shared package with a cheap provider will bottleneck a well-built site. Moving to managed WordPress hosting is usually the single biggest win, and it is worth every cent of the difference.
The second is caching. A caching plugin or server-level cache stores a finished copy of each page, so your server does not rebuild the same HTML on every visit. This one change alone often cuts load time in half. The third is images: resize them to the size they are actually displayed at, compress them, and serve them in modern formats. Images are typically the heaviest files on a page.
Finally, clean up the code. Deactivate plugins you are not using, minify CSS and JavaScript, and load scripts so they do not block the page from rendering. Fewer plugins is also faster: every plugin adds code to nearly every page.
Then measure, because guesswork wastes time. Run PageSpeed Insights and check the Core Web Vitals report in Google Search Console. If you still struggle after hosting, caching, images and code, get a performance audit from a professional rather than installing more plugins.