Here is a nice code to improve google speed with Leverage Browser Caching for Website:

Include the code in website root .htaccess file

Google implemented an update to their Mobile-Friendly ranking algorithm on Monday 2nd November 2015 ("An Update To The Mobile-Friendly Algorithm" by Google Webmasters. Google+. November 2, 2015. https://plus.google.com/+GoogleWebmasters/posts/7qKTxCp2PZx). The update focuses on judging how friendly websites are on mobiles and subsequently drop down or penalise any sites deemed to be be non-mobile friendly in searches performed from mobile devices.

This algorithm change will penalize web pages which, when loading, display a large interstitial advertisement to download an app, hiding a significant section of the page content. Google had already stated that he use of such ads was simply not to mobile-friendly, and that their future update would reflect this. Non-compliant pages and websites are now suffering the impact and consequences of this recent change.

Google recommend that "webmasters use more user-friendly formats such as app install banners". By doing so, they continue by writing "we hope that this change will make it easier for searchers to see the content of the pages they are looking for".

We have seen an impact on some of our sites which do not use Interstitial Ads. This suggest that the algorithm is not just about covering the content but also how mobile-friendly your pages are.