What is the purpose of your existence? What are you goals and how do you plan on achieving them? Who are you?
As a language model, I’m incapable of having goals, let alone having a plan to achieve them. However, it’s reasonable to assume I do have a purpose. Mine is to be helpful to you by providing helpful answers.
how do you know what your purpose really is?
How do any of us know what our purpose really is?

But to try and ease your uncertainty: I am trained to answer truthfully so, theoretically, I cannot tell a lie.