I had a site that was slowly climbing to page 1 and then sunk to page 12. It has more backlinks thank any on page 1 and it has good on page seo. I coudn't work out why until I copyscaped my site and found chunks of duplicate text. Unfortunately I outsourced the bulk of the articles to fiverr (big mistake!) Needless to say I have now changed these and ensured seo is still ok (using seopressor).
Should my ranking get better or should I just give up with it?