Having fresh content will improve your google search ranking.
Google search looks for websites that are rich in content and are constantly updated.
If your website is not updated often enough then google might think your site is outdated and may no longer be relevant to people searching google.
Updating your website often with fresh content will show your website is active and google search will also crawl your website more often and usually will index your new content faster.
The less you update your website the less google search will come around to crawl and index your website.
The more you update your website by adding fresh great content the more often google search will come around and crawl your website and index your content.
Your rankings should improve as well the more fresh your content is.
Google also loves old content and will rank older content from decades ago as well. But do keep adding fresh content to your website as it will boost rankings and improve your chances of being found in the google and other search engines.