insufficient CMS user rights/roles settings

Hello, please, is there any plugin or something which would allow me some advanced user rights management?

I am about to deploy a company site based on WP, but I am unable to figure out how to solve my usr rights requirements: I need to allow just some users to edit just some pages. That is e.g. situation like this:

• user “admin” is able to edit anything
• user “adam” is able to edit just pages “aa.php” and “bb.php”
• user “eva” is just able to make new posts (news)
• users “carlos” and “juan” are both able to edit just the page “aa.php”
• I haven’t figured out so far how to manage that in WP ??

Thanks for help!
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