how does duplicate content affect?

there is 65% duplicate content on my site i changed the setting in the yoast to remove duplicate content by noindexing urls. but still sitelinker is saying 65% duplicate content and also google cache still showing the noindexed links.

Any suggestion is highly appreciated.

I understand you are using wordpress which automatically created a lots of versions of content on different places of a website. For example, your 5 posts on homepage that are listed in gardening category will also show up on /category/gardening page hence making it duplicate content. But that is perfectly normal with wordpress and poses no harm.

If you still want to remove all the duplicate content, make sure you category and tags pages are set to noindex.

Also, give google some time so for it to recrawl your noindex tags and reflect the changes in its results. It can take days some days.