SEO Expert Needed - Paid On Results only

I need someone to help me get my extensions to the top of Google and Bing's SERP. These extensions already has first page placement on many of the keywords I am targeting. I just need top 3 to realize the full potential they are capable of. My Extensions are used on Facebook and hosted on the Chrome Web Store. We can make minor changes to the text on the description however we cannot do much for the title tag on the pages. What I want is someone that can build quality back links to help raise the extensions SERPS. Payment only upon successful rankings being achieved. I have 6 Extensions, All of them do the same thing. Two of them are in English and four others are in foreign languages. Spanish, Italian, Portuguese and French. No upfront milestones. I will only pay if you can achieve top 3 positions for my keywords. Facebook Invite All, Facebook Select All, Facebook Invite Friends, are the three main keywords I am targeting. There are also some long tails that I would like to see improved as well. Preference will be give to those that can handle foreign language SEO. Good Luck bidding.