I' am first year PhD student in CS, I have completely loose my motivation and enthusiasm for the project, and I do not enjoy anymore the philosophy of a PhD, in that context. I have to decide what I should do quit or stay and try to reverse the situation or even change the topic (actually I prefer this). I do not have any problem with my advisor, however I don't know how I can start that conversation.
I have a project in my mind, is a project that i already run in my own, but I did not have idea how to deal with that. Please advice me !! I appreciate any advice.

You need to talk to your adviser. Just be honest and say that you are really interested in this particular aspect of your work and you want to be able to spend more time on that. That may be possible, depending on how your PhD is funded.

Yes, they should respect you for your honesty. It is probable that they would rather you change the topic than end up quitting (especially if you are funded but regardless I should think).