Anyone can tell me about traffic increase

I am working with some keywords by the 4-5 months. When i starting, in that time that keyword was in rank above 400. From 2 months they come down between 60 to 80. But after it they are not being increase, only moving between 6th page to 8th page.

So can anyone suggest me how can get it on 1st page or under 20. What should do me getting under 20.

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