How to Add Contacts per Blog Category

I am a new user trying to set things up nicely. I have synced my WP website having Ninja Forms with Mautic using a third party plugin and everything seems ok.

My Blog has Categories and I will like to do 3 things:

  1. For Posts - Dynamically tag contacts coming from that post category
  2. For Pages - Insert some kind of tag in the Ninja form on thaat page
    3, Is there a way to add one contact to 2 different segments? The idea is to add each contact to the Category segment and at same time add all the contacts coming from this my website to a big segment