thanks for your respond Ramon but I didn't exactly get what I want! I know what is noindex and also know how to use robots.txt but I just don't know does google drop page bounce rate if we link to a noindex page? I mean does noindex page impact on bounce rate or because of it is noindex then it does not impact on bounce rate?

my question is:

I have a page that contains some external links, I know when visitors click on them and leave my site it hurts my bounce rate, But I have a solution for that, I am using external link redirection code, with this code after users clicking on external links they are not leaving my site and first went to some link like this: "http://mysite.com/redirect/https://externalsite.com/"

and after 10 seconds they redirect to the external site, I make this redirect page noindex and nofollow. but the question is does this noindex page can decrease my page bounce rate because users don't leave my site and first go to another page of my site. but I don't know does no-indexed page has an impact on bounce rate or my struggle is worthless