design a back-end website,i don't know which language i choose?

i have a project to design a website like this www.digistyle.com and i'm in a back-end team. i don't know how should i start and what language is the best for back-end? i asked many people some one said

php

and others said

django

i don't know anything about this languages and i should start learning from beginning. the only language i code is c#. so now i want your help to give me your experiences about back-end.