[HELP] How to deindex pages from my old website

Anyone know how to deindex pages on my website. It's already indexed and I want to reverse this.

Google's help page is written in detail. You can remove the directory from Webmastertools.

Remove URLs Tool

Delete the post. Update the sitemap. Do add Webmastertolls again.

Google then removes it.

Sorry for bad English

Two things you can do now:
1. Add noindex to the pages meta tag.
2. In Google Search Console, use Removals → New Request. This hides the URL from search results for about 6 months, but you should still add noindex if you want it removed permanently.