Friends will probably come and go, in academic or any science setting people don't tend to stick. They're hard to find and make and soon afterwards they leave. You get hardened to it, learn to keep in touch with those you know all over the world but most of all I would reccommend joining social or sports clubs, it will be your escape time when things get tough, a good stress relief and fitness aid if you pick an active sport and also a place where you can meet normal people with regular lives who can ground you when you get stuck in the little world PhD students get stuck in.
I'm in the last 6 months of a 4 year PhD and I wouldn't have lasted even then first 6 months if I hadn't immediately combed my town for sports clubs I might like.

Good luck!