Do u have a section for such words like: because, to, in, at, for....

yes. check prepositions in the following blogs:

http://sweetcoconuts.blogspot.com/2010/10/exercise-33-going-places-part-2.html
http://sweetcoconuts.blogspot.com/2010/10/exercise-31-going-places.html
http://sweetcoconuts.blogspot.com/2010/10/exercise-35-going-home.html
http://sweetcoconuts.blogspot.com/2010/03/list-of-most-frequently-used.html

Ask me anything