How do I develop my Grammar Portion?

First, do not separate and see grammar a separate component from the language we speak. Naturally, we do not focus much on learning grammar separately in either Tami, Telugu or any other native words we speak. It just comes automatically. Do listen to Elementary English Conversations from Youtube (you can search and select different learning levels) and try to make a sense out of it. You will be able to do it for sure!

Dear Yogender: Learning English requires a lot of patience, and one can only learn to speak and write English without grammar mistakes, slowly, gradually over some length of time, by remembering the corrected versions and trying best not to repeat them. Reading short story books which have a lot of "dialogues" in them is much recommended because you can learn to use those dialogues during your conversation with someone. Also, reading books helps to increase your vocabulary, which is very much necessary, both to understand as well as to impress others by using such words. Consider, for example, an Indian, who had returned from the US doing some odd job. His relatives asked him "What work did you do in the US?" The man replied, "I worked as a Rodent Exterminator." Some thought it was a BIG job. However, the one who knew English translated it for them in simple words as "he means rat killer." Haha. I gave this example just for fun but also to let you know how it could make a difference in the impact of the speech. Therefore, it is essential that you continue to get coaching with trainers who can keep correcting your grammar, and help you progress in your English Speaking and Writing standards consistently. Do not feel that the time and money spent on "coaching" is a "waste." You will definitely appreciate it someday in the future when you are able to speak English very fluently and very correctly too. It has also enabled you to accept higher responsibilities in your job. So, good luck and best wishes, Yogender. Keep going slow and steady. :) 

First of all,Understand the basics that you revised during your school days. Revise all sort of tenses.

Start using them and create sentences. Use them in your daily activities. Try to speak what you learned new during the day. This will hep you to generate a habit of revising everyday plus will improve your grammar slow and steady.

I can tell you what I did to improve my grammar skills. I started reading topics of my interest in newspapers, storybooks, blogs, grammar rules and worked on it. I have learnt a lot of things such as vocabulary build-up, making sentences and a lot about grammar. I also used to learn by watching English YouTube channels and still do. I practised grammar like voice change, narration, joining etc. Follow this, and I'm sure you'll see the result. Best of luck!