^^ The above exactly. I was an international student too and the best way to fit in and make friends is to take part in everything. The International Students' Association (ISA) are generally very supportive of internationals and it seems to be a nice community with great events all year round. There are also hundreds of societies to choose from, do sign up to lots at Freshers and don't be afraid to go along to them - everyone is in the same boat!
The uni also offers courses in English language and academic writing for international students - if you feel insecure about your English, do look into them! There's lots of info on the uni website.
Surely you speak and write pretty much fluent English to get offered a place?
Your OP is perfectly understandable for instance, it's not structured exactly how an English person would, but it's as you would expect from someone who learnt English as a second language and is pretty much fluent.
I bet the biggest challenge is your accent, a guy I work with had this problem. He just told us to tell him when he was difficult to understand so he knows where he needs to improve, maybe try this with people you become friends with to improve your speaking.