Dear Tamil,
You have a problem but good to note that you have identified the cause of it also. Therefore, what is important here is to work on removing the shortcoming.
I recommend you reading the English newspapers. Keep the dictionary besides you and as and when you come across with the difficult word, keep on checking the meaning of it.
Going further, you need to improve your grammar also. Are we not taught grammar since our school days? Then why your grammar remained so weak? It appears that you must have neglected grammar. Therefore, immediately go to the market and buy books on grammar. Even old books also will suffice purpose.
There are videos on improving English but at this stage you need improvement to reach to that level, hence I would not like to recommend these to you.
Thanks,
Dinesh Divekar