Sometimes when I check the visiting stats for my website I randomly get A LOT of traffic for one specific keyphrase from google. That same keyphrase I would have been ranked in the top 3 in google's searches, but after i get a lot of traffic (None unique), I drop to the bottom of google's first page. What gives? Also, every time I make a post, this other website comments on it with all of the words in my post and leaves a link back to its own site (how can I avoid this)? thanks
It really could be anything. Sometimes Google takes data from bounce rate and click through to measure the quality of results. If you are getting people leaving your site quickly that might be affecting your results.
Google always does it to many websites. It is not your site, just continue what you are doing and let google do the rest