How can I completely remove Yoast seo from our site

Since we installed Yoast SEO plugin, google dropped us from its index.

We used to be in the top first page in Google, now we are nowhere to be seen. Our buddypress profiles have been completely wiped out from search engines and consequently our traffic has almost halved.

We tried to uninstalling it, but it causes problems with the system. When someone shares a site article on facebook, it capture the last thumbnail from the last article that was processed by Yoast, instead of the image of the current article. So we reinstalled Yoast in order to be able to like articles and send them to facebook.