Keep in mind that native English speakers have similar difficulties in learning a foreign language. It's all part of a learning process, and it takes time and practice. :-)
I faced your problem ,I mean I don't have the native like accent because I am an Arab and I have never been taught by a native teacher and have never travelled to a foreign country-I mean a country that speaks English as a first language . Then I thought a while and said to my self it is most important to concentrate on the fluency rather than the native like pronunciation and started to work on that.As I see it it is not a big problem and it will come later as u communicate with you native English friends.
so just calm and think about things which are more important:-D
I think its not the accent that is neccessary.If you are fluent enough to conversate thats enough.
I have the problem of remembering good vocabulary. Can any one tel me how can i do that?
I do read dictionary and try to use new vocab in sentences but this also isn't helping me.
Well, to improve your pronunciation and accent, you should, as my forespeakers have just said, practice a lot. I recommend How Now Brown Cow by Mini Posnoby for RP or Pronunciation in Use published by CUP as a source of model pronunciation and practice. Another important thing is to record yourself and search for errors. It is also advisable to get yourself a Phonetics teacher to correct your recordings if you can't do it yourself.