It is partially correct, when I remove the private record rule (as mentioned in the article) , my record rule that I have created runs correctly for the group that I have created as well, but for the rest of the users, the rest of the contacts are not shown and it is incorrect for me.

I need that a specific group can only see some contacts but the rest of the users can see all the contacts as it was at the beginning.

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I should only affect a group of users, not all users.

Not exactly. I have some contacts ( suppliers), and a list of users (vendors) that should only see and have access to some suppliers, not all, but not necessarily the vendors were the ones who created the contacts, but they are already existing.