Google SEO ranking problem

Here is the problem: Our website at [login to view URL] has been ranking in the top 3 search results on Google for searches such as "imvu credits", "buy imvu credits" and even among top 10 for "imvu" for the past 3 years. Our website traffic and sales have not decreased, nor did we do drastic changes to the site. However, now our site has suddenly dropped drastically in Google searches and we don't know why. It still shows high on Bing or Duckduckgo for example, but something changed in regards to Google. I want you to figure out what may have caused that sudden drop in Google rankings, make suggestions how to fix that and tell us whatever else you happen to notice about IMVUCE in regards to SEO possibilities. When you are bidding you bid with your project price and estimated hours you plan to put into this. If your work ends up getting us back into the top 5 for Google search on "imvu credits" within the next 30 days we will pay you out another 50% success bonus on top of your project price here.