Imagine I am the last surviving human, what should I do for the civilization within the rest of my life?
Assuming you've not taken on the ability to asexually reproduce, civilization no longer will exist.  To survive, I suggest you brush up on the following skills:
* Gardening to grow your own food.
* Hunting or fishing including to know how to properly field dress your game.
* Finding safe and stable shelters to live in.

I also suggest that you get a dog to help protect your homestead and alert you to dangers.