keyword ranking

hey, folks, I have a question-related SEO for example - I have been working on a specific keyword (mouse), I have done all the major activity of SEO after 3 months the keyword shows my website on google 1st page then after 1 month the keyword move to 8th or 9th page and keyword didn't move to 1st or 2nd page and doing the same activity for last 4 months so how I can move my keyword 1st page?