My website age 3years, My present ranking- 9k keywords and monthly 2400+ visitors (According to ahrefs), with an average of 400+ keywords on google's first page. I contacted an SEO farm to more increase my ranking, they said to change the website structure, and redirect the old URL. I am worried and sure if I change the structure then I will lose the ranking and visitors. My question is there any other way to keep old content to change the structure.