I just got a 1year old cockapoo for my sister and he not eating, the first day he was walking around and ate a little dog food and water but, the next day he won't even get up as much. I tried hand feeding him some food but won't eat. I notice today that his back left isn't bending right and just lays on the floor all day. Please I need some help/ advice.

p.s I got him from the dog pound and he's kind of skinny that I can feel his bones. And will take him to the vet around 2 weeks or less.

I'd take the dog to the vet ASAP. Many vets give a free exam within a few days of adoption. Did they give you any paperwork about shots, etc?

If I'm reading correctly I am counting three days that he has eaten nothing or eaten very little.
I also assume you mean his back left "leg" isn't bending right. Was this going on when you first adopted him or is it new?
Without the benefit of any other information, re: vaccines, deworming, any testing done it is pretty hard to guide you, except to say your dog needs a vet. (Which I would have said anyway)
Was this a local shelter adoption or a private rescue?