well first of all. i seem to have a lot of problems with coming up with sentences or forming sentences in general. for example when i'm talking to americans or whatever i usually don't really know what to say. but i fully understand them!! and when i'm about to say something. it's almost as if i didn't know any words.. like. i don't know any other english words other than the basic stuff. how can i improve?? please help me. thank you
As had been said - practice. It's how native speakers of a language get good at it.
You can improve your vocabulary, comprehension and accent by watching TV shows and movies (I remember meeting Dutch kids on holiday who I thought were American as they learn so much from the screen),, and grammar and the like can come from reading. However, that ease of conversation and the speed of your recall of words just comes from talking a lot. Try finding an intermediate to advanced language class where they insist on people talking in that language all the time.