Make Website mobile-friendly and correct Google pagespeed insight errors

Our current website is failing the Google mobile test !!!! We got told, that our current theme does not support mobile friendly, so if it would be necessary to change the theme, the website must look the same as in current status. The job to make the page mobile friendly must be done on a different domain !!! After confirmation and approving, the site can be shift to its original domain. "Currently all pages are failing." Job description: 1. Make website passing Google mobile-friendly test at [login to view URL] . Errors occur: Content wider than screen Links too close together Mobile viewport not set 2. Correct all errors on Google Page speed Insights for mobiles and desktops to reach 100%. [login to view URL] [login to view URL] the moment page speed for desktops reaches 86 %. Errors: Eliminate render-blocking JavaScript and CSS in above-the-fold content Reduce server response time Leverage browser caching Minify CSS Minify JavaScript Optimize images 2.2. Page speed for mobiles only 65 % Size content to viewport Consider Fixing: Configure the viewport Size tap targets appropriately 2 Passed Rules 71 / 100Speed Should Fix: Eliminate render-blocking JavaScript and CSS in above-the-fold content Consider Fixing: Reduce server response time Leverage browser caching Minify CSS Minify JavaScript Optimize images 3. Changing 3 links in footer for emails Thank you very much