There are different methods to recover your website.
1) If your website is penalized by search engine the ways are different.
2) But If you are losing ranks due to competition than ways are different.
It is very possible that the drop is a consequence of a penalty. Penalties can be manual, or alternatively, filters may be applied algorithmically. In both instances, it is important to start taking action immediately to remove the issue.
1. Content changes need SEO : update the latest content, the most unique, should not copy special content is the image.
2. Create new posts that match current and future to build internal links.
3. Should not go low quality backlink at that time.
4. Use social networking to make Google feel more influential than other websites
It is very possible that the drop is a consequence of a penalty. Penalties can be manual, or alternatively, filters may be applied algorithmic. In both instances, it is important to start taking action immediately to remove the issue.