You need to add <meta name="robots" content="noindex, follow"> to the <head> section of all your search results pages. You want robots NOT to index pages but t

You need to add <meta name="robots" content="noindex, follow"> to the <head> section of all your search results pages. You want robots NOT to index pages but to still follow links on your search pages. Create clean sitemap.xml file and submit it to Search Console. Another way is to just canonicalize all search results pages to your search page. With Google and these things time is involved. Once it's in the index it will take time to properly clean everything up. How was the traffic before this happened? Did the website rank for any decent keyword? Sometimes when this happens the smart thing to do is to just start from scratch with a new domain. If you want more extensive help email me.