Is this the end of the manga??

Yes, they aren't going to make a third volume at all

What why? I read somewhere about this so I went here to find some news then I saw it’s completed here

Yeah, it's completed, this is just a two-part, I mean, originally it was only a one-shot, then the author decided to make another one since the one-shot manga was getting popular. That is the complete volume of Go for it Nakamura, I don't think she plans on making a third volume