Moving in with another Family Member?

Kayleigh
Last year Febuary we moved from germany to the uk. However, my sister (16 at the time) did not want to move and stayed with my grandma (she is now 18 and moving over here) I've lived in Germany all my life and it will always be home to me. 
I am now 14 (15 in March) and living with my mum and step dad. However, i'm not happy here at all, the area is horrible, the school is horrible and i don't really have friends at all. 
I've wanted to move back since the moment we got here, so my question is, what could I do? Has anyone else been in a similar situation? What are the laws etc.? 
I wasn't sure in which category to put it so i'm just going to put it here and maybe another one or two? As I am in urgent need of help. Thank you so so much for any answers, I really appreciate any help! Xx