Since this question was posted in the religious & beliefs - christianity - theology & religious discussion section, I would take a guess that you are looking for a religious explanation to your question.
Otherwise, I would say that the proper place for it would happen to be under knowledge and education - self education - knowledge and wisdom.
To answer your question, I will leave out any religious view and address it, based on sane, rational and reasoned logic. What is Mankind(Humankind) Living For?
The basic understanding of our life is to know that it is "you" the individual who is in control. It is your individual responsibility to protect your life and the life of others, through honest action.
You are to love yourself, as well as those around you. You are to create meaning and/or purpose for your own existence. If you are looking for a reason why you are here? Answer: Your parents had kids. And, Yes, it is that simple.
Thank you for your time