Celia, your written English is actually quite good - you should be proud.  I've made some minor corrections below, mostly with capitalization and preposition usage (of, at, for).  I am not familiar with the TOEFL IBT test, but is there an oral section?  If so, you should consider practicing your spoken English with a native speaker.

Hi!  My name is Celia Liu.  I'm a college student and my major is architecture.  I really like to study English, but I don't know how to improve quickly!  I have to take the TOEFL IBT test on October 31th.  Speaking is a big problem for me, so I write instead.  I don't know how to express my thoughts in english.  So friends, please give me some advice!  By the way, I am so happy to find a place to meet different people from all over the world!  To all my new friends, let us improve together!!