Improve Lighthouse score Performance (html website) in terms of: Eliminate render-blocking resources. css/bootstrap.min.css - css/responsive.css

The website speed is optimized. Rating: 77 for mobile and 97 for desktop. We are looking for someone who can improve the performance regarding the website part: Eliminate render-blocking resources. css/bootstrap.min.css - css/responsive.css - It's an html website! Speed is optimized! We are looking for a developer who can improve the CSS. Largest Contentful Paint
5.6 s this should be down < 2.5 s.